UC Davis Biological Sciences Newsletter - Spring 1998
Mobile Signal May Suppress Plant Gene ExpressionPlants may use a gene-specific, mobile signal molecule to identify, track, and destroy viral RNA molecules during a viral infection, according to a report in Science by an international group of researchers that includes Professor William Lucas of Plant Biology. The signal may be part of an underlying supracellular surveillance system that is fundamental to plant development and physiology.Studies have shown that when foreign genes, or copies of existing genes, are introduced into a plant, expression of the introduced genes and of similar existing genes may be suppressed. The result is a state called gene "cosuppression." Lucas, Richard Jorgensen from the University of Arizona in Tucson, and Ross Atkinson and Richard Forster from HortResearch in New Zealand suggest that the cosuppression state may spread through the plant when a signal molecule moves through the phloem—the plants' long-distance transport system—and from the phloem into the surrounding tissues. Once in the tissues, the signal may move from cell to cell through intercellular channels known as plasmodesmata. Systemic spread of the cosuppression state may have evolved in plants in response to viral infection. The researchers speculate that the signal is an RNA molecule derived from the suppressed gene or its transcripts. Characterization of the signal could be a breakthrough for understanding plant-pathogen interactions, they conclude. Reference: Jorgensen RA, RG Atkinson, RLS Forster, and WJ Lucas. 1998. Science 279:1486-1487.
UC Davis Biological Sciences Newsletter - Spring 1998 |