Possible involvement of phospholipase A(2) in light signal transduction ofguard cells of Commelina communis

Polyunsaturated fatty acids induce stomatal opening (Y. Lee, H. Lee, R. C. Crain, A. Lee and S. J. Kern. 1994. Cell Signal. 6: 181-186), but it is not known whether they function as second messengers in guard cells exposed to signals that open stomata. To test the hypothesis that phospholipase A(2)( PLA(2)), which produces fatty acids and lysophospholipids, is involved in l ight signal transduction in guard cells, we treated epidermal peels of Comm elina communis L. with PLA(2) inhibitors and followed the changes in stomat al apertures in response to light. Stomatal opening by white, blue, or red light was inhibited by 2-3 different PLA(2) inhibitors in concentration ran ges that have bren reported to inhibit PLA(2) activity. However, the PLA(2) , inhibitors could not block stomatal opening induced by a polyunsaturated fatty acid. These results suggest that PLA(2) functions as a signal transdu cer for both blue and red light in guard cells.