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Plant fixes its own broken
genome, researchers find
Posted March 22, 2005
Courtesy Nature
and World Science staff
In a surprising finding that challenges the conventional rules of inheritance, a new study has
found that the cress plant Arabidopsis can overwrite the genetic code that it inherits from its parents, and revert to that of its grandparents or
great-grandparents.
Robert Pruitt of Purdue University and colleagues conducted the study, published in this
week’s issue of the research journal Nature.
The newly identified process seems to be a mysterious way that organisms can fix their own accidental mutations. Although it has long been known that living things have ways to do this, the newly identified one is puzzling.
Since DNA is a double-stranded molecule, organisms are known to correct mutations in one DNA strand by using the other strand as a template. But the new study shows that
Arabidopsis plants frequently correct mutations present in both strands of DNA.
This result cannot be explained by the normal inheritance process in which genes are passed down from one generation to the next. Instead, the team proposes that cells inherit copies of their ancestral DNA in some other form, perhaps as molecules of ribonucleic acid (RNA), a close cousin of DNA.
This RNA might be used as an “emergency backup” to correct potentially dangerous mutations in the conventional genome.
The process may be a completely new way in which the plant can avoid inheriting a particular, perhaps detrimental, genetic sequence from its parents-by reverting to that of a previous generation, researchers said.
Although it was discovered in a plant, the authors raise the possibility that the same novel mechanism of inheritance may be used by other organisms.
In a related commentary in the journal, Detlef Weigel Max Planck Institute for Developmental Biology, Tuebingen, Germany and Gerd Jürgens of the University of Tuebingen call it a
“spectacular discovery.”
The researchers found that “several independent mutant strains yielded apparently normal progeny at a high frequency (a few per cent),” the pair wrote. They also showed that “this is due to precise reversion that restores the original DNA sequence.”
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