27/04/2011

Iowa - Stephen Howell, a professor of genetics, development and cell biology and former director of the Plant Sciences Institute at ISU, has conducted research with a team from the Iowa State University and a number of other institutions to discover how plants deal with stress and how this affects yield.

"We've discovered a new arm of the pathway by which plants activate a response to environmental stress," Howell revealed. Adverse environmental conditions, such as drought, flood, heat and other stresses, affect yield more than crop pests and diseases. Finding a way to maintain high yields for plants under stress is a goal of plant breeders and other agriculture stakeholders. Professor Howell said, "These are environmental stresses that the farmers can't control, they are acts of nature. And now seed companies are interested in trying to equip plants with the ability to tolerate stress."

Plant cells produce proteins and ship them to different parts of the cell. During production and shipment, these proteins move through an area of the cell called the endoplasmic reticulum (ER). Under normal conditions, these proteins are folded into their normal, healthy three-dimensional structures as they are produced. When a plant is under stress, its cells produce poorly folded or unfolded proteins. Inside the ER, a built-in, quality-control system senses this and "sets off an alarm in the cell."  

In response to the alarm, another protein (IRE1) cuts apart an important RNA molecule, but then splices it back together to create a different sequence.

The ISU team’s research reveals plants’ defence responses; sending ‘poorly folded’ proteins through cells, which bring about internal defensive measures that help them to survive, inhibits plants’ growth. Professor Howell explains, "As it turns out, responses that are activated under stress conditions actually inhibit the growth of plants," said Howell. "This allows them to conserve their energy to survive the stress conditions."

For plants in the wild, this response is a survival tactic In production agriculture crops, however, these responses reduce yields. "You don't want crop plants to [stop growing]," Howell said. "You want them to continue to grow and produce even though they are under stress." With the new understanding of this stress response pathway, Howell says, the next step may be to silence the alarm system. "What may be important is to disable some of these stress responses," said Howell. "That may make the plant be more productive under stress conditions." Seed companies are interested in switching off this alarm system in plant cells, which will result in plants which are tollerant to stress and therefore higher yielding.