Biotech Updates

Tiny Protein Helps Bacteria ‘Talk' and Triggers Defensive Response in Plants

December 16, 2011

"Just as invading armies often use coded messages to coordinate attacks on their targets, so single-celled bacteria use biological signals to communicate when they attack plants and animals," said Pamela Ronald, a UC Davis professor of plant pathology and the lead researcher on their recent study published in the journal PLoS ONE and in the journal Discovery Medicine. The research group found that bacterial gene Ax21 generates a communication signal different from other bacteria. The gene generates a shorter signal that is secreted outside the bacterium and signals other bacteria to assemble into biofilms which make the bacteria resistant to drying out and antibiotic treatment.

"Additionally, Ax21 triggers a change in the expression of nearly 500 bacterial genes, transforming the bacteria from fairly benign organisms into fierce invaders," Ronald said. "In essence, through communication and communal living, the bacteria increase their chances of survival and proliferation," she added. In rice, the bacteria multiply rapidly in the water transport system, causing the plant to wither and die.

Some rice plants have an immune receptor called XA21 that detects the Ax21 protein produced by the invading bacteria. The Ax21 protein is also present in human disease-causing bacterium. "This study demonstrates that bacteria communicate using private messages. However, plants can intercept these messages and gain a tactical advantage in the evolutionary battle," Ronald said.

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