Plants have a memory of pests that spans generations
[Via Ars Technica]
In the age of industrial agriculture, seeds are often purchased in bulk from corporate growers that use heavy doses of pesticides. They then travel many miles to a farm where climate, soil and pest conditions are dramatically different. As a result, crops often encounter new ailments that never impacted first generation seed plants, which may have been protected from the most troublesome invaders.
This might not be the best approach, based on three studies published in the February issue of Plant Physiology. Not only does adversity in the parent generation appear to make the seed stronger, but it primes plants to fight the specific ailments that plagued their parents.
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What these experiments show (and both papers are Open Access so you can read them also) is that the offspring of plants that are attacked by pests are more resistant to those pests. Something about the attack of the plants alters their genetic material in some way that gets passed onto the offspring. Even if the genetic material itself does not change.
This is what we define as epigenetic change. We are just now getting a handle on it.
Your genes are not all and exposure to environmental processes have been shown to effect epigenetic factors. Now we have direct scientific proof.
This is important stuff to understand. I’ve written about the importance of diversity in a species. As I wrote though, natural selection actually tries to drive a species towards the ‘best’ form. It removes those that don’t work and in many ways acts to reduce diversity.
Evolution depends on wide genetic diversity of a species coupled with removal of that diversity by natural selection. These contradictory steps can be easily solved by a couple of mechanisms.
One is that most mutations are not selective in the current environment. So they can be maintained and spread amongst a species. But if the environment changes, these diverse sequences may now become selective.
Thus, at the moment, height in of little consequence to human survival and it not really selected against. Unless you live in an environment of limited resources. Then small stature becomes important and selected for.
Another way it to hide a large array of diversity inside the genome but keep those genes silenced in ways to escape selection. That is apparently what is happening here.
New genes to provide resistance are not being created. The expression of genes already present are being altered. The plants have hidden a tremendous amount of diversity within their genome giving them a plasticity not seen it we look at one gene-one activity.
So some cellular process is at work here, opening up hidden genetic diversity and pathways that had not been previously available to selection.
And what is cool is that they have an initial idea of what cellular processes are involved – small RNAs.
When they used mutant plants that could not make small RNAs, the memory effect was gone. The offspring reacted just as the parents did.
The thing to recognize here is not that new mutations are involved or whole new processes. It is all still due to which genes get turned on when.
The importance of small RNAs for control of gene expression has only recently been observed. Here, for the first time, we have evidence that they represent part of an epigenetic process
We know that they can affect human metabolism. It will be interesting to see if they can affect humans across generations.
It could well be that there is actually tremendous diversity hidden in our genes just waiting for the right – or wrong – environment to present itself. And this diversity then gets expressed in our offspring.
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