CHANGES IN THE PLASMA-MEMBRANE DISTRIBUTION OF RICE PHOSPHOLIPASE-D DURING RESISTANT INTERACTIONS WITH XANTHOMONAS-ORYZAE PV ORYZAE

Phospholipase D (PLD; EC 3.1.4.4), which hydrolyzes phospholipids to g enerate phosphatidic acid, was examined in rice leaves undergoing susc eptible or resistant interactions with Xanthomonas oryzae pv oryzae. R NA analysis of leaves undergoing resistant interactions revealed diffe rent expression patterns for PLD over 5 days relative to control plant s or those undergoing susceptible interactions, By using an activity a ssay and immunoblot analysis, we identified three forms of PLD (1, 2, and 3). PLD 1 was observed only at 1 day after tissue infiltration. PL Ds 2 and 3 were detected up to 3 days in all interactions, Immunoelect ron microscopy studies revealed PLD to be associated predominantly wit h the plasma membrane. In cells undergoing a susceptible response, PLD was uniformly distributed along the plasma membrane at 3, 6, 12, and 24 hr after inoculation. However, within 12 hr after bacterial challen ge in resistant interactions, PLD was clustered preferentially in memb ranes adjacent to bacterial cells.