Abstract
The effects of molecular probes on the dynamic behaviours of O-·2 generation and α-linolenate release from rice (Oryza sativa) blade tissue preparations with press-injured spot (2mm), pre-treated with the molecular probes and post-stimulated with blast fungus (Pyricularia oryzae) elicitor, were further surveyed. Compound W-7 or ophiobolin A, potent inhibitors on the function of CaM (calmodulin), strongly inhibited both O-·2 generation at 10μM and α-linolenate release at 500μM after the elicitor stimulation. The comparative coupledenzymic analysis on the behaviour of free CaM in the healthy or infected rice blades with blast fungus conidia revealed an immediate decrease of free CaM by the infection. TPA (10μM), an agonist of diacylglycerol for proteinkinase C, did not activate both parameters with the elicitor stimulation, although TPA (10μM) markedly activated the α-linolenate release at the later phase with the stimulation. The application of H-7 (1mM) or staurosporin (10μM), unspecific inhibitors on proteinkinases, inhibited the O-·2 generation, but staurosporin (50μM) activated the α-linolenate release at the later phase and H-7 (1mM) inhibited the α-linolenate release after the elicitor stimulation. The application of 1, 2-benzisothiazol-3(2H)-one 1, 1-dioxide (1mM) with the elicitor stimulation further activated the O-·2 generation and markedly activated the α-linolenate release at the later phase. The lines of evidence strongly bore out the suggestion that the formations of Ca2+-MPs (Ca2+-calcium modulated proteins), which signal-coupled with the operation of phospholipase C system, play an indispensable role in activating rice blade O-·2 forming redox system and phospholipase A2.
