Plants fix genes using copies from ancestors

Some plants can reinstate genes missing from their own chromosomes but that had been carried by previous generations, according to a new study. These findings seem to violate genetic-inheritance laws that have been accepted for more than a century.

While studying Arabidopsis thaliana, a mustard plant commonly used in genetics experiments, Robert Pruitt and his colleagues at Purdue University in West Lafayette, Ind., found that plants showing a recessive mutation that causes deformed flowers had normal-looking offspring about 10 percent of the time. The genetics conundrum is that each deformed parent had two copies of the mutant gene, and by Mendelian inheritance laws, these parents should have passed only the mutant gene to all their offspring.

Previously, researchers who had noticed similar breeding quirks assumed that someone had contaminated the plants with pollen carrying a normal gene, says Pruitt.

He and his coworkers dismissed that conclusion by isolating the self-pollinating plants. Through a battery of tests, the researchers failed to find any copies of the normal gene in unexpected parts of the parents’ DNA. They also found that the mutant gene hadn’t undergone further mutations that changed it back to normal in the offspring with unexpectedly normal flowers.

Pruitt’s team posits in the March 24 Nature that the plants may carry some of their grandparents’ and earlier generations’ unflawed genetic code in a nucleic acid other than DNA, such as RNA.