Sensitivity to abscisic acid of guard-cell K+ channels is suppressed by abi1-1, a mutant Arabidopsis gene encoding a putative protein phosphatase (original) (raw)

1995, Proceedings of the National Academy of Sciences

Abscisic acid (ABA) modulates the activities of three major classes of ion channels-inwardand outwardrectifying K+ channels (IK,i and IK,out, respectively) and anion channels-at the guard-cell plasma membrane to achieve a net efflux of osmotica and stomatal closure. Disruption of ABA sensitivity in wilty abil-1 mutants ofArabidopsis and evidence that this gene encodes a protein phosphatase suggest that protein (de-)phosphorylation contributes to guard-cell transport control by ABA. To pinpoint the role of ABIl, the abil-1 dominant mutant allele was stably transformed into Nicotiana benthamiana and its influence on IK,ing, IK,out, and the anion channels was monitored in guard cells under voltage clamp. Compared with guard cells from wild-type and vectortransformed control plants, expression of the abil-l gene was associated with 2to 6-fold reductions in IK,out and an insensitivity of both hc,in and IK,out to 20 ,uM ABA. In contrast, no differences between control and abil-1 transgenic plants were observed in the anion current or its response to ABA. Parallel