Note: I do not work for Audiogalaxy; I am just a satisfied customer.
This legal music downloads site has a program that lets you download an unlimited number of songs from fast servers at a cheap fee per month. If you choose the cheapest (per month) option, the charge ($2.95) is automatically billed to your credit card each month until you decide to cancel.
This sounds promising. If the Linux community chooses this model, the software can remain free as in beer/speech, but downloading from the server would be charged, either per (insert period of time), or (insert each piece of software), or (insert how many megabytes downloaded). Hopefully the connections would be faster than the norm to make the additional charge appealing to consumers.
Even better, persuade the geek you'll date to use and contribute to Linux! It worked for me. Then again, my ability to persuade is more effective than most geeks. (For the reason why, check my sig.)
Perhaps this could be used in tracking down counterfiters
Well, only if the counterfiters are stupid enough to put real chips in their fake money...
Not necessarily. The authorities could check if each bill had their chip(s). That way, any bill that didn't have chip(s) in it would automatically be suspected as counterfeit.
For those of you who don't have a subscription to the Science journal, here's the article, with references:
The Closest Living Relatives of Land Plants
Kenneth G. Karol,1* Richard M. McCourt,2 Matthew T. Cimino,1 Charles F. Delwiche1
The embryophytes (land plants) have long been thought to be related to the green algal group Charophyta, though the nature of this relationship and the origin of the land plants have remained unresolved. A four-gene phylogenetic analysis was conducted to investigate these relationships. This analysis supports the hypothesis that the land plants are placed phylogenetically within the Charophyta, identifies the Charales (stoneworts) as the closest living relatives of plants, and shows the Coleochaetales as sister to this Charales/land plant assemblage. The results also support the unicellular flagellate Mesostigma as the earliest branch of the charophyte lineage. These findings provide insight into the nature of the ancestor of plants, and have broad implications for understanding the transition from aquatic green algae to terrestrial plants.
1 Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
2 Department of Botany, Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103, USA.
* To whom correspondence should be addressed. E-mail: karol@umail.umd.edu
The evolutionary origin of the embryophytes (or land plants) from their green algal ancestor was a pivotal event in the history of life. This monophyletic group has altered the biosphere and now dominates the terrestrial environment, but uncertainty as to the identity of their closest living relatives has persisted in the literature after more than a century of scrutiny (1-3). Morphological and molecular studies have identified two distinct lineages within the green plants sensu lato, termed Charophyta and Chlorophyta. The Charophyta comprise the land plants and at least five lineages (orders) of fresh water green algae, and are sister to the Chlorophyta, which consist of essentially all other green algae. Previous molecular analyses have verified monophyly of most of the charophyte orders (4-6), but branching patterns among these lineages have been only weakly supported, with results that were sensitive to taxon selection and method of phylogenetic reconstruction. Similarly, analyses of morphological and genome structural data have clarified some relationships (7-10), but have been limited by the number of characters available, uncertain homology assessment, and a lack of character independence.
Identifying the closest living relatives of land plants has been difficult. Roughly 470 million years of evolution since the colonization of the land, coupled with rapid radiation and numerous extinction events (2, 3, 11), has resulted in an inherently difficult phylogenetic problem, with much information from the early, common history of evolution obscured by subsequent evolution in the now independent lineages (12).
To investigate the evolutionary origin of land plants and identify the closest living relatives of this group, we analyzed DNA sequence data from four genes representing three plant genomes: atpB and rbcL (plastid), nad5 (mitochondrial), and the small subunit (SSU) rRNA gene (nuclear). The data set used for phylogenetic analyses excludes introns and unalignable regions for a total length of 5147 base pairs [Appendix 1 (13)] (14). We sampled 34 representative charophytes, including eight land plants, and six outgroup taxa [Appendix 2 (13)]. The data were analyzed with Bayesian inference (BI), maximum likelihood (ML), maximum parsimony (MP), and minimum evolution with two distance measures [LogDet (ME-ld) and maximum likelihood (GTR+I+ [Gamma ] ; ME-ml) distances] [Appendix 3 (13)]. Both BI and ML are probabilistic methods that utilize explicit models of sequence evolution to test phylogenetic hypotheses. Advantages of BI are that it is relatively fast and provides probabilistic measures of tree strength that are more directly comparable with traditional statistical measures than those more commonly used in phylogenetic analyses (15, 16). To measure phylogenetic stability, posterior probabilities (PP) as inferred by BI were calculated and bootstrapping was performed for the ML, MP, and ME analyses.
Using BI and ML on the combined four-gene data set (Fig. 1), we found the order Charales sister to the land plants with strong statistical support (PP = 1.0, ML = 94) and a monophyletic Coleochaetales sister to the Charales/land plant clade (PP = 1.0, ML = 59). The MP and ME analyses [Appendix 4 (13)] also support the result that Charales have a closer relationship to land plants than do Coleochaetales (MP = 80, ME-ld = 97, ME-ml = 92). The overall structure of the best tree is consistent with previous work in that the classically recognized orders were also recovered (land plants, PP = 1.0, ML = 100, MP = 100, ME-ld = 100, ME-ml = 100; Charales, PP = 1.0, ML = 100, MP = 100, ME-ld = 100, ME-ml = 100; Coleochaetales, PP = 1.0, ML = 62, MP = Fig. 1. Phylogenetic relationships for Charophyta determined by Bayesian inference from the combined four-gene data set. The maximum likelihood tree (-ln = 64499.87863) was of identical topology. Posterior probabilities are noted above branches and maximum likelihood bootstrap values are below branches. The topology is drawn with Cyanophora rooting the tree. Branch lengths are mean values and are proportional to the number of substitutions per site (bar, 0.05 substitutions/site). Taxonomy is modified from (23). [View Larger Version of this Image (41K GIF file)]
The phylogenetic placement of Mesostigma, a unicellular, scaly green flagellate has been controversial. Traditionally classified with like forms as a prasinophyte, it also has been allied with the Charophyta. The phylogenetic position of Mesostigma is critical to understanding the evolution of form and structure in the lineage that gave rise to land plants. Like the results presented here, analyses of actin sequences place Mesostigma at the base of the Charophyta (17), and analyses of SSU rRNA gene sequence data place it among them (albeit in close association with Chaetosphaeridium, a grouping not supported by other data) (5, 18). By contrast, maximum likelihood analyses of amino-acid data from both the plastid and mitochondrial genomes of Mesostigma find strong support for placement of this genus as sister to all green algae rather than as a basal charophyte lineage (19, 20). The latter analyses differ from those presented here in the number of taxa sampled (8 versus 40). When divergence times are large and internal branches short, limited taxon sampling can lead to inaccurate phylogenies (12). If taxon sampling explains this conflict, then one would predict convergence on the phylogeny presented here as additional organellar genomes become available.
Both Charales and Coleochaetales have long been considered to be close relatives of the land plants (1, 21-23). Key morphological characters uniting these three lineages include branched filamentous growth, oogamous sexual reproduction, and phragmoplastic cell division, along with a suite of ultrastructural and biochemical features (2). In light of similar morphological traits (i.e., parenchyma-like tissue, placental transfer cell wall ingrowths, and zygote retention), the genus Coleochaete and, in some instances, a single species, C. orbicularis, has been discussed as a possible sister taxon to land plants (8, 24). Our results indicate that the Coleochaetales are monophyletic and less closely related to the land plants than the Charales. Both Bayesian inference and bootstrap analyses permit evaluation of alternative hypotheses; we were unable to identify any alternative hypothesis with nontrivial support (25).
The Charales also share numerous characteristics with land plants, some of which are not found in the Coleochaetales. These include gross sperm morphology and ultrastructure (26), numerous discoidal chloroplasts per cell, protonemal filaments, complete absence of zoospores (sperm are the only flagellate cells), and encasement of the egg by sterile jacket cells (cortication) prior to fertilization (10, 21). Our data suggest that many of the similarities between Charales and land plants reflect homology rather than convergent evolution. Cortication of the zygote reminiscent of that in Charales is found in some species of Coleochaete, but occurs only after fertilization of the egg, and zygote cortication is not thought to occur in Chaetosphaeridium (10). In addition, primary plasmodesmata have been confirmed in the Charales, a character shared with land plants (27). Although plasmodesmata have been described in Coleochaete, it is unknown whether their development is primary or secondary in nature.
Identification of the Charales as the sister taxon to land plants with the Coleochaetales as sister to the Charales/land plant clade suggests that the common ancestor of land plants was a branched, filamentous organism with a haplontic life cycle and oogamous reproduction. The early stages of development in the Charales involve formation of protonemal filaments reminiscent of those found in some mosses and other land plants, which suggests that a similar heteromorphic development might have occurred in the common ancestor. Other characteristics of this ancestor, including both developmental and biochemical features, may explain not only how their descendants came to survive on land, but also how they ultimately came to dominate terrestrial ecosystems. Moreover, the charophytes have important applications in a wide range of disciplines (Charales in cell biology, Coleochaetales in ultrastructure, and Zygnematales in physiology) (10). Consequently, a robust phylogeny relating these taxa to land plants can place this work in an evolutionary context and lead to the identification and development of appropriate model systems for future studies.
Although it is tempting to envision the origin of land plants as having been from amorphous pond scum, these data indicate that the common ancestor of land plants and their closest algal relatives was a relatively complex organism. The extant Charales are the remnants of a once diverse, but now largely extinct, group which includes some of the oldest known plant fossils [roughly 420 million years ago (Ma) from the late Ordovician] (11, 28). While the fossil record for the other charophyte orders is fragmentary at best (29), the molecular phylogenetic data presented here (Fig. 1) suggest that these lineages diversified more than 470 Ma. While not species-rich, these algae hold a key position in the tree of life and, consequently, represent an important part of eukaryotic diversity.
REFERENCES AND NOTES
1. F. O. Bower, The Origin of Land Flora. A Theory Based upon the Facts of Alternation (Macmillan, London, 1908).
2. L. E. Graham, The Origin of Land Plants (Wiley, New York, 1993).
3. P. Kenrick, P. R. Crane, The Origin and Early Diversification of Land Plants, Smithsonian Series in Comparative Evolutionary Biology (Smithsonian Institution Press, Washington, DC, 1997).
4. R. L. Chapman et al., in Systematics of Plants II, D. E. Soltis, P. S. Soltis, J. J. Doyle, Eds. (Kluwer Academic, Norwell, MA, 1998), pp. 508-540.
5. B. Marin and M. Melkonian, Protist 150, 399 (1999) [ISI][Medline].
6. R. M. McCourt, et al., J. Phycol. 36, 747 (2000) [Abstract/Full Text].
7. H. J. Sluiman, Plant Syst. Evol. 149, 217 (1985) [ISI].
8. L. E. Graham, C. F. Delwiche, B. D. Mishler, Adv. Bryol. 4, 213 (1991) .
9. B. D. Mishler and S. P. Churchill, Brittonia 36, 406 (1984) [ISI].
10. L. E. Graham, L. W. Wilcox, Algae (Prentice-Hall, Upper Saddle River, NJ, 2000).
11. M. Feist, N. Grambast-Fessard, in Calcareous Algae and Stromatolites, R. Riding, Ed. (Springer-Verlag, Berlin, 1991), pp. 189-203.
12. J. Felsenstein, Syst. Zool. 27, 401 (1978) [ISI] .
13. Supplementary material is available on Science Online at www.sciencemag.org/cgi/content/full/294/5550/2351/ DC1.
14. Polymerase chain reaction (PCR) and sequencing: Total cellular DNA was isolated by the CTAB method [ J. J. Doyle and J. L. Doyle, Phytochem. Bull. 19, 11 (1987) ], UNSET method (a high-urea, SDS extraction buffer) or using the Nucleon Phytopure Plant DNA extraction kit (Amersham Pharmacia Biotech) following the manufacturer's protocol from fresh thalli growing in uni-algal condition. The genes were amplified by PCR with gene specific primers (atpB upstream: 5'-TGTTACTTGTGAAGTTCAACA-3'; atpB downstream: 5'-CTAAATAAAATGCTTGTTCAGG-3'; rbcL upstream: 5'-ATGTCACCACAAACAGAAACTAAAGC-3'; rbcL downstream: 5'-AATTCAAATTTAATTTCTTTCC-3'; nad5 upstream: 5'-GTAGGTGATTTTGGATTAGC-3': nad5 downstream: 5'-GTACCTAAACCAATCATCATATC-3'; SSU upstream: 5'-GTAGTCATATGCTTGTCTC-3': SSU downstream: 5'-CTTGTTACGACTTCTCCT-3') and sequenced using either an ABI-PRISM 377 or 3100 DNA sequencer (PE Applied Biosystems) according to the manufacturer's protocols. The resulting sequence chromatograms were edited and compiled into a single alignment using Sequencher 3.1.1 (Gene Codes Corp.) and exported in NEXUS format for phylogenetic analyses. Many published SSU rRNA gene sequences were difficult to align to published secondary structure models. Small subunit sequences that could not be matched to such structure models were resequenced for this study (13). A single intron was found in the Coleochaete orbicularis nad5 sequence and the distribution of introns in nad5 was examined in the taxa within our study. No introns were found in any other species of Coleochaete or other algal charophyte nad5 sequence sampled. Introns with the same insertion point as that of C. orbicularis were only found in Sphagnum (a moss) and Marchantia (a liverwort) which share a sequence identity of 69.39%, compared with only 37.82% and 37.81% to C. orbicularis, respectively. Anthoceros (a hornwort) has an apparently unrelated intron inserted 128 base pairs downstream with 37.35% identity with that of Sphagnum, 35.99% identity to Marchantia, and 39.46% to C. orbicularis. For comparison, pairs of random sequences with similar base composition and length as the natural sequences had an average of 37.78% sequence identity. These data suggest that the C. orbicularis nad5 intron was acquired independently from that shared by Sphagnum and Marchantia.
15. J. P. Huelsenbeck, J. P. Bollback, in Handbook of Statistical Genetics, M. Bishop, Ed. (Wiley, London, 2001).
16. J. P. Huelsenbeck, F. Ronquist, R. Nielsen, J. P. Bollback, Science 294, 2310 (2001) [Abstract/Full Text] .
17. D. Bhattacharya, K. Weber, S. S. An, W. Berning-Koch, J. Mol. Evol. 47, 544 (1998) [ISI][Medline] .
18. H. J. Sluiman and C. Guihal, J. Phycol. 35, 395 (1999) [Abstract].
19. C. Lemieux, C. Otis, M. Turmel, Nature 403, 649 (2000) [CrossRef][ISI][Medline] .
20. C. Lemieux, C. Otis, M. Turmel, in press.
21. F. E. Fritsch, The Structure and the Reproduction of the Algae (Cambridge Univ. Press, London, 1935), vol. I.
22. J. D. Pickett-Heaps and H. J. Marchant, Cytobios 6, 255 (1972) [ISI] .
23. K. R. Mattox, K. D. Stewart, in The Systematics of the Green Algae, D. E. G. Irvine, D. M. John, Eds. (Academic Press, London, 1984), pp. 29-72.
24. B. D. Mishler and S. P. Churchill, Cladistics 1, 305 (1985) .
25. Alternative hypotheses that were explored include: Coleochaete orbicularis sister to land plants, PP = 0.0, ML = 0.0%; Coleochaete sister to land plants, PP = 0.0, ML = 0.0%; Coleochaetales sister to land plants, PP = 0.0, ML = 0.0%; Coleochaetales sister to Charales, PP = 0.0, ML = 0.4%.
26. T. M. Duncan, K. S. Renzaglia, D. J. Garbary, Pl. Syst. Evol. 204, 125 (1997) .
27. M. E. Cook, L. E. Graham, C. E. J. Botha, C. A. Lavin, Am. J. Bot. 84, 1169 (1997) [Abstract] .
28. M. Feist and R. Feist, Nature 385, 401 (1997) [ISI][Medline] .
29. H. Tappan, The Paleobiology of Plant Protists (Freeman, New York, 1980).
30. We thank T. Bachvaroff, T. Cooke, G. French, M. Hibbs, J. Lewandowski, T. Marushak, and E. Zimmer for critical comments; C. Drummond, S. Snyder, and A. Zeccardi for technical assistance; J. Bollback and J. Huelsenbeck for important discussions and assistance with Bayesian analyses; M. Casanova, M. Feist, and V. Proctor for material; F. Lang et al., C. Lemieux, C. Otis, and M. Turmel for unpublished sequence data; and S. Fritz, A. Kaspar, R. Sudman, K. Sytsma, and the GPPRGC ("Deep Green"; USDA) for help with development of this project. This work was supported by NSF grant DEB-9978117 and is dedicated to the memory of C. C. Delwiche.
7 August 2001; accepted 9 November 2001
10.1126/science.1065156
Include this information when citing this paper.
Audiogalaxy has a Gold program. This program lets you download an unlimited number of songs from fast servers at a cheap fee per month. If you choose the cheapest (per month) option, the charge ($2.95) is automatically billed to your credit card each month until you decide to cancel.
This sounds promising. If the Linux community chooses this model, the software can remain free as in beer/speech, but downloading from the server would be charged, either per (insert period of time), or (insert each piece of software), or (insert how many megabytes downloaded). Hopefully the connections would be faster than the norm to make the additional charge worth the cost.
I once heard Oliver Sacks talk about somebody who had been blind their whole life (due to completely opaque cataracts, I believe). A new surgery technique restored the fellow's sight. But when he woke up from surgery, all he could see was an overwhelming mass of incomprehensible color. He couldn't distinguish faces, object, or even simple shapes.
His eyes, it turned out, were functioning perfectly. But because he has been blind during infancy, the visual parts of his brain had never developed -- he had never learned to see.
Teenagers and political fanatics have turned the Net's public forums on Slashdot into hostile electronic cesspools.
That's what you get for reading Slashdot posts at -1...
Until Katz is willing to accept that no one says brilliant things all the time, then he'll never have the nerve to read the generally higher quality posts ranked 3 and above and ignore everything else.
I can't really see any benefit to banning research and study because of what the results may bring. If we must ban technology, let us learn about what we must ban first. Let us research the ethics and science of these questions before passing judgment. We may find out that it is better to stop this technology, but it's best to let reality, not fantasy, be the reason for our decision.
Changing them is playing God, no matter whether you feel you are doing it for the good or bad of humanity.
I've never found this argument to be valid in stopping innovation. It reminds me of the story about when people protested against the airplane: If Man could fly, God would give Him wings!
I haven't heard arguments for banning airplanes after September 11. Why? Because through research, study, and experience, we have learned that using the airplane is worth the risks.
Every invention that helped humanity can be argued to be playing God. Does that mean they should be banned or not used? For example, the doctor that uses LASIK technology to better my eyesight is playing God in a way, because he is altering the results of what my genes gave me.
No one complains if a doctor does surgery to fix my deteriorating eyesight, but many people get squeamish if I want my child's genes to be altered so they don't have to worry about eventually going blind, something I must deal with as I grow older. "They could create superhumans!" Could they? Maybe. No one really knows yet, so they're banning finding out the answers-just in case.
I can't really see any benefit to banning research and study because of what the results may bring. If we must ban technology, let us learn about what we must ban first. Let us research the ethics and science of these questions before passing judgment. We may find out that it is better to stop this technology, but it's best to let reality, not fantasy, be the reason for our decision.
I find it fascinating that in America, people freak out when they hear about human cells being cloned. But in Japan, they're discussing mixing animal cells with human cells. I wonder how Americans would react to such a combination? I don't think the Religious Right would handle this issue very well.
My point remains the same: Bin Laden believes that, via torture, he can change U.S. foriegn policy, which he sees as being the chief evil in his region.
OK, I agree.
I said that it's probably not helpful to misconstrue his aims into outdated Cold War rhetoric.
Outdated Cold War rhetoric? I wasn't even alive for most of the Cold War. My point is that Osama wants his thoughts to spread, especially among other Muslims.
I also don't see the point in trying to define what religions are "twisted" and what aren't. I don't happen to believe in any of them.
Me neither.
I can't say I much love the very idea of evangelism itself: it's a pretty twisted idea to think that other people must believe what you believe.
I disagree with evangelism, too. However, I'd rather deal with the nonviolent form of evangelism that most religious people practice than Osama's.
I know some about Islam, but I'm not an expert. So I'm giving my Muslim friends the benefit of the doubt when they say Osama's actions are not Islamic, and that he's taking some things in the Koran out of context. I've witnessed a similar phenomenon with the Christian Bible in use, so I try to empathize as much as possible.
Osama bin Laden on America in Saudi countries:
"The call to wage war against America was made because America has spear-headed the crusade against the Islamic nation, sending tens of thousands of its troops to the land of the two Holy Mosques over and above its meddling in its affairs and its politics, and its support of the oppressive, corrupt and tyrannical regime that is in control. These are the reasons behind the singling out of America as a target. And not exempt of responsibility are those Western regimes whose presence in the region offers support to the American troops there."
Questions: Why doesn't America helping the Muslim Kuwaitis in Desert Storm count? Also, what about helping the Muslim Croats fight against the Eastern Orthodox Serbs in the Balkans? If you read the article, most of Osama's criticism revolves around the US' support of Israel. Is this issue really about Islam or anti-Semitism?
Osama bin Laden on spreading (his twisted version) of Islam:
"I am one of the servants of Allah. We do our duty of fighting for the sake of the religion of Allah. It is also our duty to send a call to all the people of the world to enjoy this great light and to embrace Islam and experience the happiness in Islam. Our primary mission is nothing but the furthering of this religion."
While spreading a religion is fine, I personally don't consider ObL's interpretation of Islam to be accurate or representative of the religion, as many Muslims have been telling us. That's why I say his philosophy is twisted.
If we allow these criminals to alter our way of life to the point that we cease to function, or regulate ourselves into and Orwellian nightmare then we may as well lie down and die.
Live your life as you always have.
Not only should we live normally so the terrorists don't have control, we should live normally in order to have control over the terrorists.
Think about it: If they really could blow up the US, if they really could take over, they would have done it by now. Their goal is to spread their twisted philosophy everywhere, right? So why haven't they taken control? The terrorist haven't done this because they aren't strong enough to take over the United States. So they're playing these games with Americans in order to frighten us into submission.
9/11 was the first life-altering tragedy for many Americans. Time to crawl out from under the bed. Use that fear and energy to do better in your everyday tasks than ever before. It is our way of life, our freedom, that these people want to destroy, simply because their repressive ideas can't survive long in a free American society.
Remember at the end of The Matrix, when the agents threw everything they could against Neo? Neo was untouched by the agents, because he realized how powerful he really was for the first time. The agents who weren't eliminated ran away.
I'm not requesting anyone to stop bullets in their tracks. I am requesting everyone to find the strength within them to overcome any fear or anxiety these events are provoking in us. Realize how strong you are, and you can do just about anything.
Slashdot Mirror
What are you talking about? And why should I take an AC seriously?
Note: I do not work for Audiogalaxy; I am just a satisfied customer.
This legal music downloads site has a program that lets you download an unlimited number of songs from fast servers at a cheap fee per month. If you choose the cheapest (per month) option, the charge ($2.95) is automatically billed to your credit card each month until you decide to cancel.
This sounds promising. If the Linux community chooses this model, the software can remain free as in beer/speech, but downloading from the server would be charged, either per (insert period of time), or (insert each piece of software), or (insert how many megabytes downloaded). Hopefully the connections would be faster than the norm to make the additional charge appealing to consumers.
Date a geek tonight.
Even better, persuade the geek you'll date to use and contribute to Linux! It worked for me. Then again, my ability to persuade is more effective than most geeks. (For the reason why, check my sig.)
Perhaps this could be used in tracking down counterfiters
Well, only if the counterfiters are stupid enough to put real chips in their fake money...
Not necessarily. The authorities could check if each bill had their chip(s). That way, any bill that didn't have chip(s) in it would automatically be suspected as counterfeit.
For those of you who don't have a subscription to the Science journal, here's the article, with references:
/ DC1.
The Closest Living Relatives of Land Plants
Kenneth G. Karol,1* Richard M. McCourt,2 Matthew T. Cimino,1 Charles F. Delwiche1
The embryophytes (land plants) have long been thought to be related to the green algal group Charophyta, though the nature of this relationship and the origin of the land plants have remained unresolved. A four-gene phylogenetic analysis was conducted to investigate these relationships. This analysis supports the hypothesis that the land plants are placed phylogenetically within the Charophyta, identifies the Charales (stoneworts) as the closest living relatives of plants, and shows the Coleochaetales as sister to this Charales/land plant assemblage. The results also support the unicellular flagellate Mesostigma as the earliest branch of the charophyte lineage. These findings provide insight into the nature of the ancestor of plants, and have broad implications for understanding the transition from aquatic green algae to terrestrial plants.
1 Department of Cell Biology and Molecular Genetics, University of Maryland, College Park, MD 20742, USA.
2 Department of Botany, Academy of Natural Sciences, 1900 Benjamin Franklin Parkway, Philadelphia, PA 19103, USA.
* To whom correspondence should be addressed. E-mail: karol@umail.umd.edu
The evolutionary origin of the embryophytes (or land plants) from their green algal ancestor was a pivotal event in the history of life. This monophyletic group has altered the biosphere and now dominates the terrestrial environment, but uncertainty as to the identity of their closest living relatives has persisted in the literature after more than a century of scrutiny (1-3). Morphological and molecular studies have identified two distinct lineages within the green plants sensu lato, termed Charophyta and Chlorophyta. The Charophyta comprise the land plants and at least five lineages (orders) of fresh water green algae, and are sister to the Chlorophyta, which consist of essentially all other green algae. Previous molecular analyses have verified monophyly of most of the charophyte orders (4-6), but branching patterns among these lineages have been only weakly supported, with results that were sensitive to taxon selection and method of phylogenetic reconstruction. Similarly, analyses of morphological and genome structural data have clarified some relationships (7-10), but have been limited by the number of characters available, uncertain homology assessment, and a lack of character independence.
Identifying the closest living relatives of land plants has been difficult. Roughly 470 million years of evolution since the colonization of the land, coupled with rapid radiation and numerous extinction events (2, 3, 11), has resulted in an inherently difficult phylogenetic problem, with much information from the early, common history of evolution obscured by subsequent evolution in the now independent lineages (12).
To investigate the evolutionary origin of land plants and identify the closest living relatives of this group, we analyzed DNA sequence data from four genes representing three plant genomes: atpB and rbcL (plastid), nad5 (mitochondrial), and the small subunit (SSU) rRNA gene (nuclear). The data set used for phylogenetic analyses excludes introns and unalignable regions for a total length of 5147 base pairs [Appendix 1 (13)] (14). We sampled 34 representative charophytes, including eight land plants, and six outgroup taxa [Appendix 2 (13)]. The data were analyzed with Bayesian inference (BI), maximum likelihood (ML), maximum parsimony (MP), and minimum evolution with two distance measures [LogDet (ME-ld) and maximum likelihood (GTR+I+ [Gamma ] ; ME-ml) distances] [Appendix 3 (13)]. Both BI and ML are probabilistic methods that utilize explicit models of sequence evolution to test phylogenetic hypotheses. Advantages of BI are that it is relatively fast and provides probabilistic measures of tree strength that are more directly comparable with traditional statistical measures than those more commonly used in phylogenetic analyses (15, 16). To measure phylogenetic stability, posterior probabilities (PP) as inferred by BI were calculated and bootstrapping was performed for the ML, MP, and ME analyses.
Using BI and ML on the combined four-gene data set (Fig. 1), we found the order Charales sister to the land plants with strong statistical support (PP = 1.0, ML = 94) and a monophyletic Coleochaetales sister to the Charales/land plant clade (PP = 1.0, ML = 59). The MP and ME analyses [Appendix 4 (13)] also support the result that Charales have a closer relationship to land plants than do Coleochaetales (MP = 80, ME-ld = 97, ME-ml = 92). The overall structure of the best tree is consistent with previous work in that the classically recognized orders were also recovered (land plants, PP = 1.0, ML = 100, MP = 100, ME-ld = 100, ME-ml = 100; Charales, PP = 1.0, ML = 100, MP = 100, ME-ld = 100, ME-ml = 100; Coleochaetales, PP = 1.0, ML = 62, MP = Fig. 1. Phylogenetic relationships for Charophyta determined by Bayesian inference from the combined four-gene data set. The maximum likelihood tree (-ln = 64499.87863) was of identical topology. Posterior probabilities are noted above branches and maximum likelihood bootstrap values are below branches. The topology is drawn with Cyanophora rooting the tree. Branch lengths are mean values and are proportional to the number of substitutions per site (bar, 0.05 substitutions/site). Taxonomy is modified from (23). [View Larger Version of this Image (41K GIF file)]
The phylogenetic placement of Mesostigma, a unicellular, scaly green flagellate has been controversial. Traditionally classified with like forms as a prasinophyte, it also has been allied with the Charophyta. The phylogenetic position of Mesostigma is critical to understanding the evolution of form and structure in the lineage that gave rise to land plants. Like the results presented here, analyses of actin sequences place Mesostigma at the base of the Charophyta (17), and analyses of SSU rRNA gene sequence data place it among them (albeit in close association with Chaetosphaeridium, a grouping not supported by other data) (5, 18). By contrast, maximum likelihood analyses of amino-acid data from both the plastid and mitochondrial genomes of Mesostigma find strong support for placement of this genus as sister to all green algae rather than as a basal charophyte lineage (19, 20). The latter analyses differ from those presented here in the number of taxa sampled (8 versus 40). When divergence times are large and internal branches short, limited taxon sampling can lead to inaccurate phylogenies (12). If taxon sampling explains this conflict, then one would predict convergence on the phylogeny presented here as additional organellar genomes become available.
Both Charales and Coleochaetales have long been considered to be close relatives of the land plants (1, 21-23). Key morphological characters uniting these three lineages include branched filamentous growth, oogamous sexual reproduction, and phragmoplastic cell division, along with a suite of ultrastructural and biochemical features (2). In light of similar morphological traits (i.e., parenchyma-like tissue, placental transfer cell wall ingrowths, and zygote retention), the genus Coleochaete and, in some instances, a single species, C. orbicularis, has been discussed as a possible sister taxon to land plants (8, 24). Our results indicate that the Coleochaetales are monophyletic and less closely related to the land plants than the Charales. Both Bayesian inference and bootstrap analyses permit evaluation of alternative hypotheses; we were unable to identify any alternative hypothesis with nontrivial support (25).
The Charales also share numerous characteristics with land plants, some of which are not found in the Coleochaetales. These include gross sperm morphology and ultrastructure (26), numerous discoidal chloroplasts per cell, protonemal filaments, complete absence of zoospores (sperm are the only flagellate cells), and encasement of the egg by sterile jacket cells (cortication) prior to fertilization (10, 21). Our data suggest that many of the similarities between Charales and land plants reflect homology rather than convergent evolution. Cortication of the zygote reminiscent of that in Charales is found in some species of Coleochaete, but occurs only after fertilization of the egg, and zygote cortication is not thought to occur in Chaetosphaeridium (10). In addition, primary plasmodesmata have been confirmed in the Charales, a character shared with land plants (27). Although plasmodesmata have been described in Coleochaete, it is unknown whether their development is primary or secondary in nature.
Identification of the Charales as the sister taxon to land plants with the Coleochaetales as sister to the Charales/land plant clade suggests that the common ancestor of land plants was a branched, filamentous organism with a haplontic life cycle and oogamous reproduction. The early stages of development in the Charales involve formation of protonemal filaments reminiscent of those found in some mosses and other land plants, which suggests that a similar heteromorphic development might have occurred in the common ancestor. Other characteristics of this ancestor, including both developmental and biochemical features, may explain not only how their descendants came to survive on land, but also how they ultimately came to dominate terrestrial ecosystems. Moreover, the charophytes have important applications in a wide range of disciplines (Charales in cell biology, Coleochaetales in ultrastructure, and Zygnematales in physiology) (10). Consequently, a robust phylogeny relating these taxa to land plants can place this work in an evolutionary context and lead to the identification and development of appropriate model systems for future studies.
Although it is tempting to envision the origin of land plants as having been from amorphous pond scum, these data indicate that the common ancestor of land plants and their closest algal relatives was a relatively complex organism. The extant Charales are the remnants of a once diverse, but now largely extinct, group which includes some of the oldest known plant fossils [roughly 420 million years ago (Ma) from the late Ordovician] (11, 28). While the fossil record for the other charophyte orders is fragmentary at best (29), the molecular phylogenetic data presented here (Fig. 1) suggest that these lineages diversified more than 470 Ma. While not species-rich, these algae hold a key position in the tree of life and, consequently, represent an important part of eukaryotic diversity.
REFERENCES AND NOTES
1. F. O. Bower, The Origin of Land Flora. A Theory Based upon the Facts of Alternation (Macmillan, London, 1908).
2. L. E. Graham, The Origin of Land Plants (Wiley, New York, 1993).
3. P. Kenrick, P. R. Crane, The Origin and Early Diversification of Land Plants, Smithsonian Series in Comparative Evolutionary Biology (Smithsonian Institution Press, Washington, DC, 1997).
4. R. L. Chapman et al., in Systematics of Plants II, D. E. Soltis, P. S. Soltis, J. J. Doyle, Eds. (Kluwer Academic, Norwell, MA, 1998), pp. 508-540.
5. B. Marin and M. Melkonian, Protist 150, 399 (1999) [ISI][Medline].
6. R. M. McCourt, et al., J. Phycol. 36, 747 (2000) [Abstract/Full Text].
7. H. J. Sluiman, Plant Syst. Evol. 149, 217 (1985) [ISI].
8. L. E. Graham, C. F. Delwiche, B. D. Mishler, Adv. Bryol. 4, 213 (1991) .
9. B. D. Mishler and S. P. Churchill, Brittonia 36, 406 (1984) [ISI].
10. L. E. Graham, L. W. Wilcox, Algae (Prentice-Hall, Upper Saddle River, NJ, 2000).
11. M. Feist, N. Grambast-Fessard, in Calcareous Algae and Stromatolites, R. Riding, Ed. (Springer-Verlag, Berlin, 1991), pp. 189-203.
12. J. Felsenstein, Syst. Zool. 27, 401 (1978) [ISI] .
13. Supplementary material is available on Science Online at www.sciencemag.org/cgi/content/full/294/5550/2351
14. Polymerase chain reaction (PCR) and sequencing: Total cellular DNA was isolated by the CTAB method [ J. J. Doyle and J. L. Doyle, Phytochem. Bull. 19, 11 (1987) ], UNSET method (a high-urea, SDS extraction buffer) or using the Nucleon Phytopure Plant DNA extraction kit (Amersham Pharmacia Biotech) following the manufacturer's protocol from fresh thalli growing in uni-algal condition. The genes were amplified by PCR with gene specific primers (atpB upstream: 5'-TGTTACTTGTGAAGTTCAACA-3'; atpB downstream: 5'-CTAAATAAAATGCTTGTTCAGG-3'; rbcL upstream: 5'-ATGTCACCACAAACAGAAACTAAAGC-3'; rbcL downstream: 5'-AATTCAAATTTAATTTCTTTCC-3'; nad5 upstream: 5'-GTAGGTGATTTTGGATTAGC-3': nad5 downstream: 5'-GTACCTAAACCAATCATCATATC-3'; SSU upstream: 5'-GTAGTCATATGCTTGTCTC-3': SSU downstream: 5'-CTTGTTACGACTTCTCCT-3') and sequenced using either an ABI-PRISM 377 or 3100 DNA sequencer (PE Applied Biosystems) according to the manufacturer's protocols. The resulting sequence chromatograms were edited and compiled into a single alignment using Sequencher 3.1.1 (Gene Codes Corp.) and exported in NEXUS format for phylogenetic analyses. Many published SSU rRNA gene sequences were difficult to align to published secondary structure models. Small subunit sequences that could not be matched to such structure models were resequenced for this study (13). A single intron was found in the Coleochaete orbicularis nad5 sequence and the distribution of introns in nad5 was examined in the taxa within our study. No introns were found in any other species of Coleochaete or other algal charophyte nad5 sequence sampled. Introns with the same insertion point as that of C. orbicularis were only found in Sphagnum (a moss) and Marchantia (a liverwort) which share a sequence identity of 69.39%, compared with only 37.82% and 37.81% to C. orbicularis, respectively. Anthoceros (a hornwort) has an apparently unrelated intron inserted 128 base pairs downstream with 37.35% identity with that of Sphagnum, 35.99% identity to Marchantia, and 39.46% to C. orbicularis. For comparison, pairs of random sequences with similar base composition and length as the natural sequences had an average of 37.78% sequence identity. These data suggest that the C. orbicularis nad5 intron was acquired independently from that shared by Sphagnum and Marchantia.
15. J. P. Huelsenbeck, J. P. Bollback, in Handbook of Statistical Genetics, M. Bishop, Ed. (Wiley, London, 2001).
16. J. P. Huelsenbeck, F. Ronquist, R. Nielsen, J. P. Bollback, Science 294, 2310 (2001) [Abstract/Full Text] .
17. D. Bhattacharya, K. Weber, S. S. An, W. Berning-Koch, J. Mol. Evol. 47, 544 (1998) [ISI][Medline] .
18. H. J. Sluiman and C. Guihal, J. Phycol. 35, 395 (1999) [Abstract].
19. C. Lemieux, C. Otis, M. Turmel, Nature 403, 649 (2000) [CrossRef][ISI][Medline] .
20. C. Lemieux, C. Otis, M. Turmel, in press.
21. F. E. Fritsch, The Structure and the Reproduction of the Algae (Cambridge Univ. Press, London, 1935), vol. I.
22. J. D. Pickett-Heaps and H. J. Marchant, Cytobios 6, 255 (1972) [ISI] .
23. K. R. Mattox, K. D. Stewart, in The Systematics of the Green Algae, D. E. G. Irvine, D. M. John, Eds. (Academic Press, London, 1984), pp. 29-72.
24. B. D. Mishler and S. P. Churchill, Cladistics 1, 305 (1985) .
25. Alternative hypotheses that were explored include: Coleochaete orbicularis sister to land plants, PP = 0.0, ML = 0.0%; Coleochaete sister to land plants, PP = 0.0, ML = 0.0%; Coleochaetales sister to land plants, PP = 0.0, ML = 0.0%; Coleochaetales sister to Charales, PP = 0.0, ML = 0.4%.
26. T. M. Duncan, K. S. Renzaglia, D. J. Garbary, Pl. Syst. Evol. 204, 125 (1997) .
27. M. E. Cook, L. E. Graham, C. E. J. Botha, C. A. Lavin, Am. J. Bot. 84, 1169 (1997) [Abstract] .
28. M. Feist and R. Feist, Nature 385, 401 (1997) [ISI][Medline] .
29. H. Tappan, The Paleobiology of Plant Protists (Freeman, New York, 1980).
30. We thank T. Bachvaroff, T. Cooke, G. French, M. Hibbs, J. Lewandowski, T. Marushak, and E. Zimmer for critical comments; C. Drummond, S. Snyder, and A. Zeccardi for technical assistance; J. Bollback and J. Huelsenbeck for important discussions and assistance with Bayesian analyses; M. Casanova, M. Feist, and V. Proctor for material; F. Lang et al., C. Lemieux, C. Otis, and M. Turmel for unpublished sequence data; and S. Fritz, A. Kaspar, R. Sudman, K. Sytsma, and the GPPRGC ("Deep Green"; USDA) for help with development of this project. This work was supported by NSF grant DEB-9978117 and is dedicated to the memory of C. C. Delwiche.
7 August 2001; accepted 9 November 2001
10.1126/science.1065156
Include this information when citing this paper.
Audiogalaxy has a Gold program. This program lets you download an unlimited number of songs from fast servers at a cheap fee per month. If you choose the cheapest (per month) option, the charge ($2.95) is automatically billed to your credit card each month until you decide to cancel.
.02 from a Computer/Business person.
This sounds promising. If the Linux community chooses this model, the software can remain free as in beer/speech, but downloading from the server would be charged, either per (insert period of time), or (insert each piece of software), or (insert how many megabytes downloaded). Hopefully the connections would be faster than the norm to make the additional charge worth the cost.
Just
I'm sorry, I meant At First Sight.
Strange I got a blind man's story mixed up with a bank robber story...
I once heard Oliver Sacks talk about somebody who had been blind their whole life (due to completely opaque cataracts, I believe). A new surgery technique restored the fellow's sight. But when he woke up from surgery, all he could see was an overwhelming mass of incomprehensible color. He couldn't distinguish faces, object, or even simple shapes.
His eyes, it turned out, were functioning perfectly. But because he has been blind during infancy, the visual parts of his brain had never developed -- he had never learned to see.
The movie Out of Sight is based on Sack's story. I highly recommend watching the film.
Teenagers and political fanatics have turned the Net's public forums on Slashdot into hostile electronic cesspools.
That's what you get for reading Slashdot posts at -1...
Until Katz is willing to accept that no one says brilliant things all the time, then he'll never have the nerve to read the generally higher quality posts ranked 3 and above and ignore everything else.
I can't really see any benefit to banning research and study because of what the results may bring. If we must ban technology, let us learn about what we must ban first. Let us research the ethics and science of these questions before passing judgment. We may find out that it is better to stop this technology, but it's best to let reality, not fantasy, be the reason for our decision.
I've never found this argument to be valid in stopping innovation. It reminds me of the story about when people protested against the airplane: If Man could fly, God would give Him wings!
I haven't heard arguments for banning airplanes after September 11. Why? Because through research, study, and experience, we have learned that using the airplane is worth the risks.
Every invention that helped humanity can be argued to be playing God. Does that mean they should be banned or not used? For example, the doctor that uses LASIK technology to better my eyesight is playing God in a way, because he is altering the results of what my genes gave me.
No one complains if a doctor does surgery to fix my deteriorating eyesight, but many people get squeamish if I want my child's genes to be altered so they don't have to worry about eventually going blind, something I must deal with as I grow older. "They could create superhumans!" Could they? Maybe. No one really knows yet, so they're banning finding out the answers-just in case.
I can't really see any benefit to banning research and study because of what the results may bring. If we must ban technology, let us learn about what we must ban first. Let us research the ethics and science of these questions before passing judgment. We may find out that it is better to stop this technology, but it's best to let reality, not fantasy, be the reason for our decision.
I find it fascinating that in America, people freak out when they hear about human cells being cloned. But in Japan, they're discussing mixing animal cells with human cells. I wonder how Americans would react to such a combination? I don't think the Religious Right would handle this issue very well.
My point remains the same: Bin Laden believes that, via torture, he can change U.S. foriegn policy, which he sees as being the chief evil in his region.
OK, I agree.
I said that it's probably not helpful to misconstrue his aims into outdated Cold War rhetoric.
Outdated Cold War rhetoric? I wasn't even alive for most of the Cold War. My point is that Osama wants his thoughts to spread, especially among other Muslims.
I also don't see the point in trying to define what religions are "twisted" and what aren't. I don't happen to believe in any of them.
Me neither.
I can't say I much love the very idea of evangelism itself: it's a pretty twisted idea to think that other people must believe what you believe.
I disagree with evangelism, too. However, I'd rather deal with the nonviolent form of evangelism that most religious people practice than Osama's.
I know some about Islam, but I'm not an expert. So I'm giving my Muslim friends the benefit of the doubt when they say Osama's actions are not Islamic, and that he's taking some things in the Koran out of context. I've witnessed a similar phenomenon with the Christian Bible in use, so I try to empathize as much as possible.
Is Osama's belief about American intervention or his version of Islam?
It's both. Read Osama's interview in 1998.
Osama bin Laden on America in Saudi countries:
"The call to wage war against America was made because America has spear-headed the crusade against the Islamic nation, sending tens of thousands of its troops to the land of the two Holy Mosques over and above its meddling in its affairs and its politics, and its support of the oppressive, corrupt and tyrannical regime that is in control. These are the reasons behind the singling out of America as a target. And not exempt of responsibility are those Western regimes whose presence in the region offers support to the American troops there."
Questions: Why doesn't America helping the Muslim Kuwaitis in Desert Storm count? Also, what about helping the Muslim Croats fight against the Eastern Orthodox Serbs in the Balkans? If you read the article, most of Osama's criticism revolves around the US' support of Israel. Is this issue really about Islam or anti-Semitism?
Osama bin Laden on spreading (his twisted version) of Islam:
"I am one of the servants of Allah. We do our duty of fighting for the sake of the religion of Allah. It is also our duty to send a call to all the people of the world to enjoy this great light and to embrace Islam and experience the happiness in Islam. Our primary mission is nothing but the furthering of this religion."
While spreading a religion is fine, I personally don't consider ObL's interpretation of Islam to be accurate or representative of the religion, as many Muslims have been telling us. That's why I say his philosophy is twisted.
Coulda fooled me.
French rig factor with explosives
Teen killed with explosives in Northern Ireland
Violence erupts in Macedonia
And that's just off 1 news site today.
If we allow these criminals to alter our way of life to the point that we cease to function, or regulate ourselves into and Orwellian nightmare then we may as well lie down and die.
Live your life as you always have.
Not only should we live normally so the terrorists don't have control, we should live normally in order to have control over the terrorists.
Think about it: If they really could blow up the US, if they really could take over, they would have done it by now. Their goal is to spread their twisted philosophy everywhere, right? So why haven't they taken control? The terrorist haven't done this because they aren't strong enough to take over the United States. So they're playing these games with Americans in order to frighten us into submission.
9/11 was the first life-altering tragedy for many Americans. Time to crawl out from under the bed. Use that fear and energy to do better in your everyday tasks than ever before. It is our way of life, our freedom, that these people want to destroy, simply because their repressive ideas can't survive long in a free American society.
Remember at the end of The Matrix, when the agents threw everything they could against Neo? Neo was untouched by the agents, because he realized how powerful he really was for the first time. The agents who weren't eliminated ran away.
I'm not requesting anyone to stop bullets in their tracks. I am requesting everyone to find the strength within them to overcome any fear or anxiety these events are provoking in us. Realize how strong you are, and you can do just about anything.
Rebel against the terrorists. Live normally.
I tried your link and got a 404 message-the page doesn't exist. Could you check this out so I can read the article? Thanks.