Steroids to bulk food crops?

Soy, corn, rape seed and wheat, among others, are the raw materials for a host of ingredients used across a wide range of applications by food manufacturers. But because crops are vulnerable to climatic conditions, prices remain exposed, and frequently translate as squeezed margins for their key buyers, the ingredients firms. Treating plants with steroids could offer performance enhancement by boosting the biomass and seed yields of crops, say scientists. Unfortunately, plant steroids are complex, expensive chemicals, and the biological mechanisms by which they alter plant growth and development have remained largely a mystery. Two new research articles by Howard Hughes Medical Institute investigator Joanne Chory and her colleagues claim to open up a new pathway to understanding how plant steroids work at the molecular level. They claim the discoveries may one day lead to less expensive ways to trigger growth enhancement of plants. "The common theme of these two articles is that we are now beginning to unravel the molecular mechanisms by which steroid hormones regulate gene expression in plants," said Chory. The first study reveals how plant steroid hormones, called brassinosteroids, plug into and activate receptor proteins on the surface of plant cells. Receptor activation is the first step in triggering processes, such as growth, development, the stress response and senescence - the deterioration of plants at the end of a growing season. In a second study, the researchers identified and clarified the function of specific transcription factors, which are proteins that regulate genes involved in the cell's response to steroids. According to the US researchers, these experiments hinted that one important steroid-related gene coded for a receptor protein called BRI1 that bound to the cell membrane. Their experiments indicated that another protein, a kinase called BIN2, appeared to act negatively in the steroid pathway to modify BES1 and BZR1 proteins, which targeted these proteins for turnover. In the presence of the steroids, BIN2 becomes inactivated by an unknown mechanism, thereby allowing BES1 and BZR1 to accumulate in the nucleus of the plant cell. "Although we've known about BRI1 for almost eight years, we hadn't shown that it was actually a steroid receptor and not just part of a bigger complex," said Chory. She claims that demonstrating that the steroid binds to BRI1 will open the way to new studies of the structural details of the interaction. "We will aim to obtain a three-dimensional structure of this receptor both with and without the steroid attached," said Chory. "And once we do that, we can begin to understand how this binding transmits signals inside the cell." The researchers reported their findings in articles published in the 13 January 2005, issue of Nature and the28 January 2005, issue of Cell .

Steroids to bulk food crops?

Fundamental research could bring added bulk to crop harvests used extensively by the food industry.

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