Plants May Be Able To Correct Mutated Genes 363
ddutt writes "NY Times is running a story that talks of an exciting new discovery, which, if confirmed, could represent an unprecedented exception to Mendel's
laws of inheritance. The discovery involves.. 'plants that possess a corrected version of a defective gene inherited from both their parents, as if some handy backup copy with the right version had been made in the grandparents' generation or earlier.'"
Also on New Scientist (Score:5, Informative)
New Scientist has coverage. No registration required.
http://www.newscientist.com/article.ns?id=dn7185 [newscientist.com]
J. Wolfgang Goerlich
No, not really (Score:5, Informative)
Now, this is definitely a pretty cool discovery, and there's going to be a stampede of people hunting around looking for some sort of, say, RNA copy of the genome hiding somewhere in Arabidopsis, and there will be a lot of fun in epigenetics. But it isn't going to destroy evolutionary theory, although I expect creationists (excuse me, "intelligent design theorists") will be running around for decades insisting that because this phenomenon exists, it's impossible for mutations to happen.
Read the Proper FA (Score:2, Informative)
Beware, there are pictures of MUTANT plants here. Watch out for the triffids.
the plants don't actually "correct" mutations... (Score:5, Informative)
What was reported is that although there were mutations in the DNA of the plant, its siblings didn't have them anymore. The researcher said that the best theory at the moment is that the non-mutated DNA was coming from the RNA of the plant. IANAB, but I think RNA usually is though to serve only a functional "middle man" role betweeen the genetic code and the cell machinery, and not actively involved in reproduction...
He did not say that the plant was actively fixing its DNA for its offspring.
The non-mutated RNA was itself directly inherted from the parents. In a way the RNA has become a bad backup copy of the DNA. That's the present theory... I guess this is what they'll start looking for... "Bad backup copy" since still 90% of the offspring of the plant still contained the mutated DNA.
Re:Sex bias in reporting? (Score:1, Informative)
Re:How this impacts evolutionary theory (Score:5, Informative)
An organism repairing it's own DNA is not unheard of. There are certain somatic (IE: not passed down from generation to generation) mutations and other varieties of DNA damage that lead to cancer. There is a mechanism in place to replace these mutations with another copy. The body also has a way of detecting and removing some viruses and retroviruses that have embedded themselves in the DNA of the host organism, to a limited extent.
Same story, no reg (Score:2, Informative)
Plants Challenge Genetic Inheritance Laws [yahoo.com]
Re:How this impacts evolutionary theory (Score:3, Informative)
Lets take a common human example: syckle-cell anemia.
Syckle-Cell is a mutation in the blood cells which causes them to be deformed and clog capillaries (amoung other things). The condition is fatal without treatment. However, having sycle-cell anemia also makes one resistant to malaria. How is this helpful?
If someone has only one gene for syckle-cell (they are heterozygous recessive), they are resistant to malaria but the anemia wont kill them. If they have both bad genes (they are homozygous recessive), they die of the anemia. If they are homozygous dominant (both functional genes), they die of malaria. In malaria hot-zones, you get a lot of heterozygous recessive individuals and a lot of children dying of one condition or the other.
Now, imagine that you had a mechanism to correct a deleterous mutation, but *only* if the mutation is homozygous. A homozygous dominant individual dies of malaria. A heterozygous recessive individual is mildly affected by the anemia but is protected from malaria. A homozygous recessive individual is *corrected to heterozygous* and is thereby protected from malaria without dying of anemia! You have a fourth of affected children dying instead of half.
Plants may use this to end up with a stable heterozygous population for deleterious mutations which have some benefit, say a root hair deformation which nevertheless protects from parasites. This can actually speed up genetic drift by preserving mutations which might otherwise die out. In the malaria example above, it is common for human populations to quickly lose the gene if the malaria threat is removed. In the case where a corrective mechanism exists, the anemia would not be as harmful and might stay in the population longer (for the next outbreak).
Not only does this not invalidate current ideas of evolution, it is obvious how a critter with such a mechanism would quickly have an advantage.
Re:Sex bias in reporting? (Score:3, Informative)
Sigh. Pruitt is last author. In the bio-sciences, this means that he's the principle investigator - the guy with the lab, the guy with the money, the boss, the big cheese. More to the point, he's listed on the Nature paper as the contact person. You know, the person to talk to if you're wrighting a story? There are *plenty* of PI's who are female - if something happens in their lab, they're the ones who get to talk to the press.
All of the comments in the NYT writeup are from male scientists.
That's because you get quotes from the authorities in the field - those people who have the most experience. The ones with 20-30 years of experience. The ones who got their Ph.D. in the 70's or before. When there wasn't a lot of female graduate students.
Your complaints are like saying that the CEO of a company shouldn't be quoted in news stories because all of the work to make the company sucessful is performed by others.
Could just be Plasmids (Score:2, Informative)
However, a good controlled experiment should be able to rule this out, and I'm sure we'll all be talking about this in Biochem labs here at the UW this week.
Re:How this impacts evolutionary theory (Score:2, Informative)
From the article:
A mutated gene can be put right by various mechanisms that are already known, but all require a correct copy of the gene to be available to serve as the template. The Purdue team scanned the DNA of the entire arabidopsis genome for a second, cryptic copy of the hothead gene but could find none.
They then go on to say they suspect RNA of holding the backup copy somehow. But (as the article mentions) RNA is unstable and unsuitable for holding data for any decent amount of time.
IANAB (I will be one soon), but I suspect there is something they overlooked. For instance, when they 'scanned the genome', they probably scanned the online version (database). If they sequenced the genome of their particular plant, they'll find a backup copy.
Re:Intelligent Design (Score:1, Informative)
Re:How this impacts evolutionary theory (Score:5, Informative)
The thing that's so remarkable about this case is as you said: BOTH alleles of the gene of the plant were defective as inherited from their parents, and yet they somehow reverted to an allele from the grandparents, across the entire organism. According to current theory, sexual replication causes a kid to inherit one allele of each gene from each parent (and by "theory", I mean you can watch this happen under a microscope). If both alleles received are "faulty" (which is a sticky term to use in many cases), there's no known way for a newly fertilized cell to know this. There's no information about what the correct gene should look like except the two copies of the gene it has. In cancer, as you point out to address the parent post, there is always a source of information used to correct the mutation.
In the case of UV damage, information exists in the form of two fused thimidine molecules (two T's). If a cell sees two fused T's, it has a repair mechanism for correcting them. But, importantly, if this mistake is not corrected before DNA duplication occurs, then random bases are paired with the T's, because they're damaged. Once this happens, each daughter cell has lost the information required to correct the problem, and the mutation persists. If this happens in an unlucky spot, you can get melanoma.
In the case of other more serious damage, like double-stranded breaks, your cell pulls in the other copy of your genes and edits against that. The information needed for repair is the "good" copy of the allele in the sister chromosome.
So you can see why this is so confusing -- in the case in the article the daughter cells, with two bad alleles for the gene they studied, are supposed to have no information pointing them to the gene from the grandparents. And yet they did, since they were able to fix it. The article postulates that this could be because a THIRD copy of the gene exists as RNA that's passed down from the grandparents (third since there are two chromosomes, each with a copy of the gene). If this were true, then the RNA would be the source of information required to fix the problem. Alternatively, there could be a specific protein that hunts down mutations in this gene and somehow fixes it, since it somehow bonds only to the correct version of the gene. But that's just my wild speculation.
Re:So what happens to gentically modified plants? (Score:5, Informative)
That's not mutation as you've described, it's natural and artificial selection, but so long as there are unmodifed plants in the same areas as the GE ones, it tends to work that way, as the vast majority of GE features are disadvantagious under natural selection, and a lot of them are so disadvantagious they require real rigor to preserve via artificial selection. They're like Pekinese dogs in the wild.
Re:Also on New Scientist (Score:2, Informative)
Not exactly suprising (Score:2, Informative)
Re:Sex bias in reporting? (Score:3, Informative)
Re:Order of credit (Score:2, Informative)
Oh wait, I wrote all the analysis code. Weeee. I guess I qualify for "going to the meetings."
Seriously, I don't think all labs work that way. You'll have the PI get the last spot on the paper, and usually the person who did the most work get one of the first spots. Unless you work with a bunch of credit stealing a-holes, then it's time to work somewhere else.
And the anonymous URL is... (Score:1, Informative)
http://www.nytimes.com/2005/03/23/science/23gen
Re:Planet RAID. (Score:2, Informative)