Plant steroids offer new paradigm for how hor...( Stanford CASteroids bulk up plants j...)

Stanford, CASteroids bulk up plants just as they do human athletes, but the playbook of molecular signals that tell the genes to boost growth and development in plant cells is far more complicated than in human and animal cells. A new study by plant biologists at the Carnegie Institution used an emerging molecular approach called proteomics to identify key links in the steroid signaling chain. Understanding how these plant hormones activate genes could lead not only to enhanced harvests but also to new insights into how steroids regulate growth in both plant and animal cells.

The study by Zhi-Yong Wang and Wenqinag Tang of the Carnegie Institution's Department of Plant Biology with seven co-authors* is published in the July 25 issue of Science magazine.

Plant steroids, called brassinosteroids, are key hormones throughout the plant kingdom. They regulate many aspects of growth and development, and mutants deficient in brassinosteroids are often extremely stunted and infertile. Brassinosteroids are similar in many respects to animal steroids, but appear to function very differently at the cellular level. Animal cells respond to steroids using internal receptor molecules within the cells nucleus, whereas in plants the receptors are anchored to the outside surface of the cell membranes. A challenge for researchers has been to piece together the steps by which the hormonal signal is transmitted from the cell surface receptor to its action in the nucleus, where genes are the targets of regulation. Traditionally, genetic methods have been used to identify several components of the BR signaling pathway. However, genetic approach cannot identify all the components of a signaling pathway largely because of genetic redundancy (many genes play the same role in the cell).

To identify the links in the signal transduction chain, the researchers used the techniques of proteomics. "Proteomics is analogous to genomics," says Wang. "In genomics,
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