Transcriptional and post-translational control of the plant plasma membrane H +-ATPase by mechanical treatments

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The activity of the plant plasma membrane (PM) H +-ATPase was studied with fresh, cut or aged tissues of sugar beet ( Beta vulgaris L.) leaves. The rate of acidification of the medium by tissue samples was strongly stimulated by ageing, but unaffected by cutting. The proton-pumping activity and the specific activity of the hanadate-sensitive ATPase of purified PM vesicles prepared from aged tissues were much higher than that of fresh tissues, whereas cutting had no effect. Yet, both ageing and cutting increased the amount of PM H +-ATPase vetected by enzyme-linked immunosorbent assays. Likewise, both ageing and cutting increased the levels of pma4 and pma2 ATPase transcripts, as assayed with the corresponding probes from Nicotiana plumbaginifolia. Ageing increases, within a few hours, the levels of the transcripts, the translation and the activity of several PM H +-ATPase families. Cutting, which represents a milher mechanical stress, only increases the levels of the transcripts and their translation, without vetectable effect on the activity at the biochemical or physiological level, which suggests a post-translational control of this activity. Thus, upon mechanical stress, the activity of the H +-ATPase, a key enzyme of the plant PM is rapidly and tightly regulated by transcriptional and post-translational controls.