Salicylic acid (SA) is a hormone produced by plants that plays a key role in plant defense responses, including systemic acquired resistance (SAR). Kumar and Klessig purified a high-affinity SA-binding protein (SABP2) and cloned the encoding gene from tobacco. Recombinant SABP2 expressed in bacteria had SA-stimulated lipase activity. Inhibition of SABP2 expression by RNA interference resulted in impaired development of SAR in response to infection with tobacco mosaic virus, including suppressed stimulation of expression of the defense gene PR-1 and increased viral replication. Future studies should determine if SABP2 is the SA receptor and what role the lipase activity plays in SA signaling.
D. Kumar, D. F. Klessig, High-affinity salicylic acid-binding protein 2 is required for plant innate immunity and has salicylic acid-stimulated lipase activity. Proc. Natl. Acad. Sci. U.S.A. 100, 16101-16106 (2003). [Abstract] [Full Text]