The role of the plasma membrane H+-ATPase in defensive lignification in wheat

In order to identify a role for the plasma membrane (PM) H+-ATPase in defen sive lignification in wheat leaves the effects of various elicitors and H+- ATPase inhibitors on PM H+-ATPase activity and H+-pumping in membrane vesic les were investigated. In addition, the effects of these treatments on the lignification response were assessed by monitoring inducible phenylalanine ammonia-lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD) activities, us eful marker enzymes for lignification, and by Past Red GG, a histochemical stain for lignin. The elicitors, chitin, chitosan and N-acetyl-chitooligosa ccharide (GlcNAc)(4), had little direct effect on either PM H+-ATPase activ ity or on H+-pumping in membrane fractions. In contrast, all three treatmen ts induced increases in PAL and CAD activities and elicited lignin depositi on at wound margins. The ATPase inhibitors, vanadate and erythrosin B, had an inhibitory effect on PM H+-ATPase activity and H+-pumping, and induced i ncreases in PAL, CAD and lignification. K252a, an inhibitor of the phosphol ipid Ca2+ ion-dependent protein kinase, was a patent elicitor of PAL and CA D and also was capable of eliciting lignin deposition.