Involvement of phospholipase C-independent calcium-mediated abscisic acid signalling during Arabidopsis response to drought
2009
Cousson, A.,CEA, Saint-Paul-lez-Durance (France). Lab. des Echanges Membranaires et Signalisation
The present study investigated whether Ca2+ mobilization independent of phosphoinositide-specific phospholipase C (PI-PLC) would delay wilting in Arabidopsis thaliana cv. Columbia through mediating stomatal closure at abscisic acid (ABA) concentrations rising beyond a drought-specific threshold value. In wild type epidermis, the PI-PLC inhibitor (U73122) affected the stomatal response to 20 microM ABA but not to 30 microM ABA. Disruption in GTP-binding protein alpha subunit 1 (GPA1) affected the stomatal response to 30 microM ABA, but not to 20 microM ABA. In the gpa1-4 mutant, the inhibitory effects of the Ca2+ buffer, 1,2-bis(0-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), the inactive mastoparan analogue, mas17, and the antagonist of cyclic ADP-ribose synthesis, nicotinamide, were differentially attenuated on 30 microM ABA-induced stomatal closure. By contrast, the NADPH oxidase atrbohD/F double mutation fully suppressed inhibition of 20 microM ABA-induced stomatal closure by BAPTA or U73122 as well as inhibition of 30 microM ABA-induced stomatal closure by BAPTA, mas17 or nicotinamide. On the contrary, The Al resistant alr-104 mutation modulated ABA-induced stomatal closure by a stimulatory effect of U73122 and an increased sensitivity to mas17, nicotinamide and BAPTA. Compared to WT, the atrbohD/F double mutant was more hypersensitive than the gpa1-4 mutant to wilting under the tested water stress conditions, whereas wilting was delayed in the alr-104 mutant. Since the atrbohD/F mutation breaks down ABA-induced Ca2+ signalling through fully preventing apoplastic Ca2+ to enter into the guard cells, these results showed that a putative guard cell GPA1-dependent ADP-ribosyl cyclase activity should contribute to drought tolerance within PI-PLC-independent-Ca2+-mediated ABA signalling.
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