Plants Challenge Genetic Inheritance Laws

Plants Challenge Genetic Inheritance Laws

By JOSEPH B. VERRENGIA, AP Science Writer

Challenging a scientific law of inheritance that has stood for 150 years, scientists say plants sometimes select better bits of DNA in order to develop normally even when they inherited genetic flaws from their predecessors.

The conclusion by Purdue University molecular biologists contradicts at least some basic rules of plant evolution that were believed to be absolute since the mid-1800s when Austrian monk Gregor Mendel experimented with peas and saw that traits — good or bad — are passed on from one generation to the next. Mendelian genetics has been the foundation of both crop hybridization and the understanding of basic cell mutations and trait inheritance.

In the Purdue experiment, researchers found that a plant belonging to the mustard and watercress family sometimes corrects the genetic code it inherited from its flawed parents and grows normally like its unflawed grandparents and other ancestors.

Scientists said the discovery raises questions of whether humans also have the potential for avoiding genetic flaws or even repairing them, although the plant experiments did not directly address the possibility in higher organisms. They said the actual proteins responsible for making these fixes probably would be different in animals, if the capacity exists at all.

Details of the experiments appear in Thursday's issue of the journal Nature.

"This means that inheritance can happen more flexibly than we thought," said Robert Pruitt, the paper's senior author.

The Purdue experiments were conducted on Arabidopsis thaliana, a member of the watercress and mustard family that is commonly grown in the lab, but is not planted commercially.

Researchers found that in 10 percent of Arabidopsis thaliana plants with two copies of a mutant gene called "hothead" didn't always blossom with deformed flowers like their parents, which carried the mutant genes. Instead, those plants had normal white flowers like their grandparents, which didn't carry the hothead gene. So the deformity appeared only for a single, previous generation.

The scientists believe the plants with hothead genes appear to have kept a copy of the genetic coding from the grandparent plants and used it as a template to grow normally, perhaps when living conditions are not ideal.

However, Pruitt's team didn't find the template in the plants' DNA or chromosomes where genetic information is stored and they did not determine whether a particular gene is encoded to carry out the recovery of the normal DNA.

Finding where the normal genetic template is stored and determining how it is triggered will take additional research and probably involve more genes, Pruitt said.

Humans and other animals do not carry the hothead gene, so if this process occurs in higher organisms it must use a different trigger, he said.

The research was funded by the National Science Foundation (news - web sites). The Purdue team submitted their preliminary lab observations and requested additional funding in 2002. But NSF program director Rita A. Teutonico said the proposal initially was rejected because the review panel "thought it was a mistake."

The researchers submitted it for a second review six months later and she decided to fund the experiment despite lingering doubts. The subsequent experiments took about 18 months.

"They had to rule out every possibility of contamination," Teutonico said.

For now, she said additional experiments probably will be conducted on plants to fully describe the genetic template. But experiments on mice and other organisms could be funded in parallel with the plant tests, she said.

Other scientists described the result as "spectacular" because it reveals a novel way in which the genome can heal itself.

Detlef Weigel and Gerds Jurgen of the Max Planck Institute for Developmental Biology in Germany wrote in an accompanying commentary in Nature that the mechanism for recovering the normal DNA in the plants might be lurking in the plant's RNA, which carries out genetic orders in cells, but is less stable than DNA.

In case anyone was wondering why I put it in this subject, the thought came to me. What if the same thing happened in herps? It's possible.

I wish humans had the ability to regenerate lost body parts.