Summer 2003

Standing tall
By Susan Steeves

A research staple
Specific plant applications intrigue all the researchers working with Arabidopsis, which is also related to canola, cabbage, Brussels sprouts and broccoli. But scientists are aware the plant’s secrets may play a big role in all organisms.

“If you’re asking specifically about plant cell wall development, then it will be applicable only to plants,” says biochemist Joe Ogas. “But by framing the question in the context of understanding the basic mechanisms of molecular assembly of complex structures, there are some general lessons that might be applicable to animal systems.”

Ogas studies plants’ transition from a seed to a seedling. His research team identified a mutant in Arabidopsis in which the root of the plant continues to express embryonic traits after the rest of the plant matures. The mutant is called pickle (pkl), named for the root’s appearance. Researchers cloned the corresponding gene, PKL, and discovered it encodes a protein called CHD3, a member of a large family of proteins also found in human cells.

“Evidence from biochemistry in animal systems indicates CHD3 proteins are involved in turning off genes,” says Ogas. “If a plant doesn’t have PKL, then it can’t turn off genes that promote the embryonic state.”

Ogas says the protein functions in a roughly equivalent manner in the development of plants and people, as a factor that turns off stage-specific genes. Roots mired in the embryonic stage produce vegetable oil, just as a seed does. While it would be economically difficult to use oil-producing roots to increase yield and lower cost, Ogas has another strategy. “If we can identify regulators of oil accumulation from the mutant pickle root, we can then over express these positive regulators in seeds and convince them to make even more oil,” he says.

Crop improvement is paramount for one of Purdue’s newest Arabidopsis researchers, Matt Jenks of the horticulture and landscape architecture department (HLA). He knew as an undergraduate that he wanted to work with plants. In graduate school, he decided to pursue his goal through molecular research.

“I started studying mutants in sorghum but couldn’t easily clone the genes I wanted to study, so I switched to Arabidopsis,” Jenks says. Now he searches for genes that control the formation of plants’ outer layer, the cuticle, and the waxes that lie within it. Waxes, in particular, play an important role in plant resistance to drought because they create a hydrophobic barrier to water loss. They also provide a barrier to pathogens and insects.

If Jenks can genetically control the amount of wax produced, it may lead to plants that can grow in arid areas that currently won’t support them or make plants more resistant to insects and pathogens.

Several other Purdue Agriculture researchers use Arabidopsis to further their studies:

• David Salt (HLA) is studying ways to manipulate plants’ accumulation of metal in order to clean up hazardous material sites and also to develop plants rich in micronutrients essential for human health.
• Ray Bressan and Mike Hasegawa (HLA) collaborate in searching for genes and proteins that enable plants to tolerate stresses, such as high soil salinity, cold and drought.
• Testfay Mengiste (botany and plant pathology) researches how to increase plant resistance to pathogens such as Botrytis cinerea, a fungus that invades crops and even grows on strawberries in the refrigerator.
• Kashchandra Raghothama (HLA) investigates the genetic basis of plants’ use of phosphorus with the aim of making plants that more efficiently use the nutrient so crops can grow in soils deficient in phosphorus.

The little plant has staked out a place for itself in agricultural research at Purdue. “Arabidopsis is becoming a major Indiana crop,” Murphy chuckles. “Its sprouts taste OK; but its real value is in the contributions it’s making to science.”

 
 
© 2003 Purdue University College of Agriculture