Knowing the molecular chain of command -- how the hormone acts to influence genetic events that govern development at the cellular level -- gives scientists a way to reshape the steroid pathway to develop plants that grow in specified ways.
"We might be able to dwarf grass and keep it green by limiting brassinosteroids or increase the yield of rice by having more brassinosteroids in seeds," Chory said. Another recent study by Makoto Matsuoka's group in Japan, she said, showed that limiting brassinosteroids in rice affected leaf angle and improved yield in densely planted fields.
Vert and Chory's work helps trace a molecular pathway that is ancient -- perhaps more than a billion years old -- in both plants and animals. "Remarkably, steroid biosynthetic enzymes are highly conserved from plants to metazoans (animals), suggesting that the use of steroids as hormones preceded the plant-animal split over a billion years ago," Chory explained.
In animals, the route steroid hormones use to exert their influence in the nucleus of a cell, where gene expression is regulated, is direct, through the use of nuclear receptors. Plants, said Chory, don't have nuclear receptors, which would provide more direct access to the nucleus. Rather, plant steroids are perceived outside the cell by the extracellular domain of a cell surface receptor. Perception then regulates genetic events in the nucleus in a more roundabout way, similar to a well-studied pathway in animals known as the Wnt signaling pathway. Wnt is a secreted molecule that influences the nucleus of a cell through cell surface receptors to regulate cell-to-cell interactions and many of the events of embryogenesis in metazoans.
"Because one of the brassinosteroid signaling components w
Source:Howard Hughes Medical Institute