Playing on plants' own genetic material to breed-in desirable traits

Research into the way living cells manage their proteins has revealed a far wider range of natural genetic variation in plants and animals than traditional breeders have realized. This opens the prospect of breeding into crops such desirable traits as resistance to drought or insects by using the plants' own genetic material, rather than inserting genes from such alien species as bacteria into our food.

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It also helps explain an enduring evolutionary mystery – how organisms sometimes develop new advantageous traits quickly under changed environmental conditions rather than adapting slowly. And it may help explain the poorly understood fact that temperature determines whether hatchlings of some reptiles such as crocodiles and turtles are male or female.

Christine Queitsch and Susan Lindquist at the Whitehead Institute for Biomedical Research in Cambridge, Mass., and Todd Sangster at the University of Chicago outlined these prospects last May in the journal Nature. Dr. Lindquist, Whitehead's director, updated their report during a science-writers' seminar in Cambridge last week.

While genetic information in an organism's cells specifies the forms and traits that organism can express, it does not dictate them directly. Cells translate that information into proteins. These, in turn, shape the organism. A cell makes a large variety of proteins to carry out many biological jobs. To maintain order in what could be chaos, some proteins act as chaperons. They keep other proteins in check until it is appropriate for them to act.

One particular chaperon with the unglamorous name Hsp90 plays a key role. It "mother hens" proteins involved in the development and regulation of an organism's traits. This prevents proteins from acting when they represent genetically determined traits that would not be useful to the organism in its present environment. Since no member of the organism's species is expressing those traits, natural (or human) selection does not eliminate the relevant genes from the population. A wide range of genetic variability can then accumulate in a species unseen by the environment and unknown to plant and animal breeders.

Breeders would have a powerful tool if they could get at that variability. Lindquist says manipulating Hsp90 may do the trick. Her lab is studying the effect of lowering the concentration of Hsp90 in cells so there aren't enough chaperons to keep track of all their charges. A range of unsuspected traits have already appeared in fruit flies and the plant arabidopsis. Most would be harmful to the organisms. But some could be useful under favorable environmental conditions.

In nature, environmental stress could also impair Hsp90's chaperon action. In this way, a changed environment could release the full genetic potential of species to allow rapid adaptation to new conditions. Changes in chaperon function at different temperatures may even be involved in establishing sex in turtles. But Lindquist calls that speculative.

But she says that it now does seem certain that manipulation of Hsp90 is a potentially powerful way to get at an organism's natural genetic variability. Yet it will take a good deal more research to shape that potential into a practical tool for breeding better crops.