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Plasma membrane (PM) H+-ATPase is crucial for light-induced stomatal opening and phosphorylation of a penultimate residue, Thr948 (pen-Thr, numbering according to Arabidopsis AHA1) is required for enzyme activation. In this study, a comprehensive phosphoproteomic analysis using guard cell protoplasts from Vicia faba shows that both red and blue light increase the phosphorylation of Thr881, of PM H+-ATPase. Light-induced stomatal opening and the blue light-induced increase in stomatal conductance are reduced in transgenic Arabidopsis plants expressing mutant AHA1-T881A in aha1–9, whereas the blue light-induced phosphorylation of pen-Thr is unaffected. Auxin and photosynthetically active radiation induce the phosphorylation of both Thr881 and pen-Thr in etiolated seedlings and leaves, respectively. The dephosphorylation of phosphorylated Thr881 and pen-Thr are mediated by type 2 C protein phosphatase clade D isoforms. Taken together, Thr881 phosphorylation, in addition of the pen-Thr phosphorylation, are important for PM H+-ATPase function during physiological responses, such as light-induced stomatal opening in Arabidopsis thaliana. Comprehensive phosphoproteomic analysis using guard cell protoplasts revealed that Thr881 phosphorylation in addition of a penultimate residue, Thr948 of plasma membrane H+-ATPase are important for its function and light-induced stomatal opening. [ABSTRACT FROM AUTHOR]

Stomata in the plant epidermis open in response to light and regulate CO2 uptake for photosynthesis and transpiration for uptake of water and nutrients from roots. Light-induced stomatal opening is mediated by activation of the plasma membrane (PM) H+-ATPase in guard cells. Overexpression of PM H+-ATPase in guard cells promotes light-induced stomatal opening, enhancing photosynthesis and growth in Arabidopsis thaliana. In this study, transgenic hybrid aspens overexpressing Arabidopsis PM H+-ATPase (AHA2) in guard cells under the strong guard cell promoter Arabidopsis GC1 (AtGC1) showed enhanced light-induced stomatal opening, photosynthesis, and growth. First, we confirmed that AtGC1 induces GUS expression specifically in guard cells in hybrid aspens. Thus, we produced AtGC1::AHA2 transgenic hybrid aspens and confirmed expression of AHA2 in AtGC1::AHA2 transgenic plants. In addition, AtGC1::AHA2 transgenic plants showed a higher PM H+-ATPase protein level in guard cells. Analysis using a gas exchange system revealed that transpiration and the photosynthetic rate were significantly increased in AtGC1::AHA2 transgenic aspen plants. AtGC1::AHA2 transgenic plants showed a>20% higher stem elongation rate than the wild type (WT). Therefore, overexpression of PM H+-ATPase in guard cells promotes the growth of perennial woody plants. [ABSTRACT FROM AUTHOR]

Stomatal guard cells (GCs) are highly specialized cells that respond to various stimuli, such as blue light (BL) and abscisic acid, for the regulation of stomatal aperture. Many signaling components that are involved in the stomatal movement are preferentially expressed in GCs. In this study, we identified four new such genes in addition to an aluminum-activated malate transporter, ALMT6 , and GDSL lipase, Occlusion of Stomatal Pore 1 (OSP1), based on the expression analysis using public resources, reverse transcription PCR, and promoter-driven β-glucuronidase assays. Some null mutants of GC-specific genes evidenced altered stomatal movement. We further investigated the role played by ALMT6, a vacuolar malate channel, in stomatal opening. Epidermal strips from an ALMT6- null mutant exhibited defective stomatal opening induced by BL and fusicoccin, a strong plasma membrane H+-ATPase activator. The deficiency was enhanced when the assay buffer [Cl–] was low, suggesting that malate and/or Cl– facilitate efficient opening. The results indicate that the GC-specific genes are frequently involved in stomatal movement. Further detailed analyses of the hitherto uncharacterized GC-specific genes will provide new insights into stomatal regulation. [ABSTRACT FROM AUTHOR]

Plasma membrane H+-ATPase is thought to mediate hypocotyl elongation, which is induced by the phytohormone auxin through the phosphorylation of the penultimate threonine of H+-ATPase. However, regulation of the H+-ATPase during hypocotyl elongation by other signals has not been elucidated. Hypocotyl elongation in etiolated seedlings of Arabidopsis thaliana was suppressed by the H+-ATPase inhibitors vanadate and erythrosine B, and was significantly reduced in aha2-5, which is a knockout mutant of the major H+-ATPase isoform in etiolated seedlings. Application of the phytohormone ABA to etiolated seedlings suppressed hypocotyl elongation within 30 min at the half-inhibitory concentration (4.2 µM), and induced dephosphorylation of the penultimate threonine of H+-ATPase without affecting the amount of H+-ATPase. Interestingly, an ABA-insensitive mutant, abi1-1, did not show ABA inhibition of hypocotyl elongation or ABA-induced dephosphorylation of H+-ATPase. This indicates that ABI1, which is an early ABA signaling component through the ABA receptor PYR/PYL/RCARs (pyrabactin resistance/pyrabactin resistance 1-like/regulatory component of ABA receptor), is involved in these responses. In addition, we found that the fungal toxin fusiccocin (FC), an H+-ATPase activator, induced hypocotyl elongation and phosphorylation of the penultimate threonine of H+-ATPase, and that FC-induced hypocotyl elongation and phosphorylation of H+-ATPase were significantly suppressed by ABA. Taken together, these results indicate that ABA has an antagonistic effect on hypocotyl elongation through, at least in part, dephosphorylation of H+-ATPase in etiolated seedlings. [ABSTRACT FROM AUTHOR]

Stomatal opening, which is mediated by blue light receptor phototropins, is driven by activation of the plasma membrane H+-ATPase via phosphorylation of the penultimate threonine in the C-terminus and subsequent binding of a 14-3-3 protein. However, the biochemical properties of the protein kinase and protein phosphatase for H+-ATPase are largely unknown. We therefore investigated in vitro phosphorylation and dephosphorylation of H+-ATPase. H+-ATPase was phosphorylated in vitro on the penultimate threonine in the C-terminus in isolated microsomes from guard cell protoplasts of Vicia faba. Phosphorylated H+-ATPase was dephosphorylated in vitro, and the dephosphorylation was inhibited by EDTA, a divalent cation chelator, but not by calyculin A, an inhibitor of type 1 and 2A protein phosphatases. Essentially the same results were obtained in purified plasma membranes from etiolated Arabidopsis seedlings, indicating that a similar protein kinase and phosphatase are involved in plant cells. Further analyses revealed that phosphorylation of the H+-ATPase is insensitive to K-252a, a potent inhibitor of protein kinase, and is hypersensitive to Triton X-100, a non-ionic detergent. Moreover, dephosphorylation required Mg2+ but not Ca2+, and protein phosphatase was localized in the 1% Triton X-100-insoluble fraction. These results demonstrate that a protein kinase–phosphatase pair, K-252a-insensitive protein kinase and Mg2+-dependent type 2C protein phosphatase, co-localizes at least in part with the H+-ATPase in the plasma membrane and regulates the phosphorylation status of the penultimate threonine of the H+-ATPase. [ABSTRACT FROM PUBLISHER]

Increase of crop yield is always the desired goal, manipulation of genes in relation to plant growth is a shortcut to promote crop yield. The plasma membrane (PM) H+-ATPase is the plant master enzyme; the energy yielded by ATP hydrolysis pumps H+ out of cells, establishes the membrane potential, maintains pH homeostasis and provides the proton-motive force required for transmembrane transport of many materials. PM H+-ATPase is involved in root nutrient uptake, epidermal stomatal opening, phloem sucrose loading and unloading, and hypocotyl cell elongation. In this review, we summarize the recent progresses in roles of PM H+-ATPase in nutrient uptake and light-induced stomatal opening and discuss the pivotal role of PM H+-ATPase in crop yield improvement and its potential application in agricultural production by modulating the expression of PM H+-ATPase in crops. • Structure and post-translational regulatory of PM H+-ATPase. • Contribution of PM H+-ATPase in nutrient uptake and stomatal opening. • Increase of rice grain yield in the paddy field by PM H+-ATPase overexpression. [ABSTRACT FROM AUTHOR]