A Bifurcating Pathway Directs Abscisic Acid Effects on Stomatal Closure and Opening in Arabidopsis

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Science  14 Apr 2006:
Vol. 312, Issue 5771, pp. 264-266
DOI: 10.1126/science.1123769

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Terrestrial plants lose water primarily through stomata, pores on the leaves. The hormone abscisic acid (ABA) decreases water loss by regulating opening and closing of stomata. Here, we show that phospholipase Dα1 (PLDα1) mediates the ABA effects on stomata through interaction with a protein phosphatase 2C (PP2C) and a heterotrimeric GTP-binding protein (G protein) in Arabidopsis. PLDα1-produced phosphatidic acid (PA) binds to the ABI1 PP2C to signal ABA-promoted stomatal closure, whereas PLDα1 and PA interact with the Gα subunit of heterotrimeric G protein to mediate ABA inhibition of stomatal opening. The results reveal a bifurcating signaling pathway that regulates plant water loss.

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