PHO1 expression in guard cells mediates the stomatal response to abscisic acid in Arabidopsis

Département de Biologie Moléculaire Végétale, Biophore, Université de Lausanne, CH-1015 Lausanne, Switzerland CEA/CNRS, Laboratoire de Biologie du Développement des Plantes, UMR 7265, Université Aix-Marseille, St Paul Lez-Durance F-13108, France Institute for Molecular Plant Physiology and Biophysics, University Würzburg, Julius-von-Sachs Platz 2, D-97082 Würzburg, Germany.
The Plant Journal (Impact Factor: 5.97). 05/2012; 72(2):199-211. DOI: 10.1111/j.1365-313X.2012.05058.x
Source: PubMed


Stomatal opening and closing are driven by ion fluxes that cause changes in guard cell turgor and volume. This process is, in turn, regulated by environmental and hormonal signals, including light and the phytohormone abscisic acid (ABA). Here, we present genetic evidence that expression of PHO1 in guard cells of Arabidopsis thaliana is required for full stomatal responses to ABA. PHO1 is involved in the export of phosphate into the root xylem vessels and, as a result, the pho1 mutant is characterized by low shoot phosphate levels. In leaves, PHO1 was found expressed in guard cells and up-regulated following treatment with ABA. The pho1 mutant was unaffected in production of reactive oxygen species following ABA treatment, and in stomatal movements in response to light cues, high extracellular calcium, auxin, and fusicoccin. However, stomatal movements in response to ABA treatment were severely impaired, both in terms of induction of closure and inhibition of opening. Micro-grafting a pho1 shoot scion onto wild-type rootstock resulted in plants with normal shoot growth and phosphate content, but failed to restore normal stomatal response to ABA treatment. PHO1 knockdown using RNA interference specifically in guard cells of wild-type plants caused a reduced stomatal response to ABA. In agreement, specific expression of PHO1 in guard cells of pho1 plants complemented the mutant guard cell phenotype and re-established ABA sensitivity, although full functional complementation was dependent on shoot phosphate sufficiency. Together, these data reveal an important role for phosphate and the action of PHO1 in the stomatal response to ABA.

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Available from: Alain Vavasseur, Oct 21, 2014
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    • "Interestingly, ABA-dependent regulation of stomatal closure responds to mutation of the phosphate transporter PHO1 and the vacuolar H+-ATPase subunit A (Zimmerli et al., 2012; Zhang et al., 2013). Again, these results support interaction and co-regulation of ion homeostasis in guard cells via ion transport, ABA signaling, and regulation of stomatal aperture (Zimmerli et al., 2012; Zhang et al., 2013). Intriguingly, the transporter ZIFL1 (Induced Facilitator-Like 1) mediates potassium fluxes and has a dual function in regulating both cellular auxin transport and stomatal closure (Remy et al., 2013). "
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    • "AthPHO1; H10 was reported to be induced by numerous stresses, including local wounding responses [15,16]. Recently, AthPHO1 has been suggested to play an important role in the stomatal response to abscisic acid (ABA); its expression in guard cells is induced by ABA treatment [17]. Therefore, plant PHO1 genes have undergone a functional diversification and acquired diverse roles beyond Pi transport and homeostasis. "
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