A Bifurcating Pathway Directs Abscisic Acid Effects on Stomatal Closure and Opening in Arabidopsis Girish Mishra,* Wenhua Zhang,* Fan Deng, Jian Zhao, Xuemin Wang 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 D1 (PLD1) mediates the ABA effects on stomata through interaction with a protein phosphatase 2C (PP2C) and a heterotrimeric GTP-binding protein (G protein) in Arabidopsis. PLD1-produced phosphatidic acid (PA) binds to the ABI1 PP2C to signal ABA-promoted stomatal closure, whereas PLD1 and PA interact with the G subunit of heterotrimeric G protein to mediate ABA inhibition of stomatal opening. The results reveal a bifurcating signaling pathway that regulates plant water loss.
Department of Biology, University of Missouri, St. Louis, MO 63121, USA, and Donald Danforth Plant Science Center, St. Louis, MO 63132, USA.
* These authors contributed equally to this work.
To whom correspondence should be addressed. E-mail: wangxue@umsl.edu
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G Protein Regulation of Ion Channels and Abscisic Acid Signaling in Arabidopsis Guard Cells Xi-Qing Wang,1 Hemayet Ullah,2 Alan M. Jones,2 Sarah M. Assmann1*
The phytohormone abscisic acid (ABA) promotes plant water conservation by decreasing the apertures of stomatal pores in the epidermis through which water loss occurs. We found that Arabidopsis thaliana plants harboring transferred DNA insertional mutations in the sole prototypical heterotrimeric GTP-binding (G) protein subunit gene, GPA1, lack both ABA inhibition of guard cell inward K+ channels and pH-independent ABA activation of anion channels. Stomatal opening in gpa1 plants is insensitive to inhibition by ABA, and the rate of water loss from gpa1 mutants is greater than that from wild-type plants. Manipulation of G protein status in guard cells may provide a mechanism for controlling plant water balance.
1 Biology Department, Pennsylvania State University, 208 Mueller Laboratory, University Park, PA 16802-5301, USA. 2 Department of Biology, University of North Carolina, Chapel Hill, NC 27599-3280, USA.
* To whom correspondence should be addressed. E-mail: sma3@psu.edu
