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Tree's Leaves Genetically Different From Its Roots
ananyo writes "Black cottonwood trees (Populus trichocarpa) can clone themselves to produce offspring that are connected to their parents by the same root system. Now, after the first genome-wide analysis of a tree, it turns out that the connected clones have many genetic differences, even between tissues from the top and bottom of a single tree. 'When people study plants, they'll often take a cutting from a leaf and assume that it is representative of the plant's genome,' says Brett Olds, a biologist at the University of Illinois at Urbana-Champaign who was involved in the study. 'That may not be the case. You may need to take multiple tissues.' The finding also challenges the idea that evolution only happens in a population rather than at an individual level. As one tree contains many different genomes, natural selection and evolution could happen within a single organism."
The grafting of fruit trees is very common.
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http://youaskandy.com/questions-answers/25-article-series-1950/16332--why-do-we-have-to-graft-fruit-trees.html ,into peach stock growing in looses sandy soil. So we get peaches and plums growing where they have never grown before.
There are other advantages to grafting. A grafted fruit tree may be made to grow in new places. A peach likes sandy, wellsanded soil. The plum tree likes poorly drained soil. Peach can be grafted onto plum stock growing in soggy soil. Plum can be grafted
Grafting also helps to keep down plait pests and disease. Some fruit trees cannot be hurt by this pest or that disease. These trees form fine stock, though the fruit may be poor,.
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Sounds like that's what they're saying. Different tissues reproduce in different ways. For example a tree can make seeds or produce offshoots from the roots. One way could be more successful than another so areas with different genes within a single tree could produce a differing number of offspring.
That's essentially what cancer is, a genetic mutation in a cell that evolves it into an undying, eternally reproducing organism that parasitically gets its nutrients from its host organism/ancestor.
Actually, yes. That's exactly it. Think about the times you've seen a tree with a plenty of leaves, but with dead branches mixed in.
Given the way that trees grow, this actually makes sense. Tissues in the trunk are only grown in a very narrow band located between the bark and the wood. If a mutation happens at some point during the tree's growth, it's possible that the new tissues will be more/less likely to survive given the current environmental circumstances. Those new tissues carrying beneficial mutations would be more common as the tree continues to grow. Leaves are an even more extreme example. If a given branch has tissues with a given mutation, the leaf buds on the tree will carry it, and the leaves will carry it. Branches with more productive leaves will live longer/better as a result. Given that trees can grow for hundreds of years, it's possible that the same tree may have had dozens of mutations in its genetic structure some of which were passed on to branches at different points in time, multiple of which could still be 'active' as a result.
This is less likely to be the case for animals, since their tissues undergo complete replacement over a comparatively short period of time. That means a genetic sample from an animal would almost always only reflect the *current* genetic state of the animal.
Some marmosets are naturally chimeric some substantial portion of the time. This leads to wacky fun for researchers because it is perfectly possible(depending on how the different cell populations ended up distributed in the mature monkey) for an individual to show one genotype on blood tests; but produce offspring that appear to be genetic descendants of their brother or sister....
Just to be sure, we'll probably have to homogenize any animals and/or small children we wish to study in the future.
A mutation could happen in single cell, ar a group of cells during the tree growth, and then a leaf or an entire branch spawns from this cell.
If cells in tree nodes are for some reason likely to be the subject of mutations, it's easy to imagine natural selection occuring at a cell level, with a branch growing from the fittest cells.
But not quite impossible, interestingly.
So called Clonally transmissible cancers are particularly growth-oriented cells from some progenitor organism that managed to beat the odds and, instead of just killing their luckless host as cancers tend to, spread to other members of the species.
There is also Henrietta Lacks; but she lives more or less exclusively in laboratory environments and might not be said to count...
I think it's more of immune systems than reproductive systems.
Trees do not have "active" immune systems like animals, that cause "transplant rejection". The tree needs leaves and it needs roots, but as long as the leaves do reasonably "leafy" stuff they could be genetically different and the rest of the tree will go on fine. That's why you can often graft the top of one tree species onto the bottom part of another tree.
In contrast it's not trivial to put a related human's kidney into another human. You'd likely still have to suppress the immune system.
It could be because a tree doesn't need as much per in terms of resources (energy etc) per mass/volume, and it doesn't need to move. So some inefficiencies due to "cancer" (strange growths) are less likely to kill the tree. Thus it does not need to kill cancer as urgently.
Whereas strange growths are likely to kill you - once they are large enough so you can't move about, feed or breathe you're going to die.
Well what they are really saying is that the upper parts of a tree can diverge from each other and from their root stocks via natural methods.
Any orchard owner knows that its easy to graft dissimilar branches on a common root stock, producing, for example, two different types of apples from the same tree. Its easy, and farmers have been doing it for years. Who knows where this idea arose.
Now it turns out that nature can do roughly the same thing, without all the cutting and splicing, but rather, by gene mutation or cross pollination or what ever.
Clearly every seed germinates to a single plant, but over time, it appears that significant divergence can take place on a single living tree. This might be a significant evolutionary advantage, as some branches may survive frost, drought, or pests better than other branches. A built in diversity in a single tree.
Perhaps we have to start thinking of some of these trees as colonies of organisms rather than a single individual.
Sig Battery depleted. Reverting to safe mode.
While that is a good point, that an active immune system would prevent genetic diversification within an individual, the diversification alone is not sufficient for evolution within an individual. For example, if you had some chimeric human where your arm had genetic differences from the rest of you, regardless of how viable or not the abilities of your arm are, that genetic material will not get passed on (some slashdotters should have experimentally figured out by now that hand-person relationships do not produce viable offspring). The only impact the genetic material in the arm could have is to promote or restrict the genome possessed by the reproductive organs.
In principle, a tree branch can compete with another branch in the same tree for light, nutrients, and be capable of producing its own seeds. Or at least it could produce more branches from its side of the tree, unlike say an organ in more complex animals being able to produce more organs if successful enough.