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Murviel-lès-Montpellier, France

Li G.,CNRS Biochemistry and Plant Molecular Physiology Laboratory | Li G.,Shandong Academy of Agricultural Sciences | Boudsocq M.,Institute des science du Vegetal | Boudsocq M.,French National Institute for Agricultural Research | And 6 more authors.
Plant, Cell and Environment | Year: 2015

The hydraulic conductivity of plant roots (Lpr) is determined in large part by the activity of aquaporins. Mechanisms occurring at the post-translational level, in particular phosphorylation of aquaporins of the plasma membrane intrinsic protein 2 (PIP2) subfamily, are thought to be of critical importance for regulating root water transport. However, knowledge of protein kinases and phosphatases acting on aquaporin function is still scarce. In the present work, we investigated the Lpr of knockout Arabidopsis plants for four Ca2+-dependent protein kinases. cpk7 plants showed a 30% increase in Lpr because of a higher aquaporin activity. A quantitative proteomic analysis of wild-type and cpk7 plants revealed that PIP gene expression and PIP protein quantity were not correlated and that CPK7 has no effect on PIP2 phosphorylation. In contrast, CPK7 exerts a negative control on the cellular abundance of PIP1s, which likely accounts for the higher Lpr of cpk7. In addition, this study revealed that the cellular amount of a few additional proteins including membrane transporters is controlled by CPK7. The overall work provides evidence for CPK7-dependent stability of specific membrane proteins. Plant aquaporins that are critical regulators of root water transport are regulated by phosphorylation. However the knowledge of protein kinases acting on aquaporin function is still scarce. In the present work, by combining physiological measurements of root water transport with quantitative proteomics we identified CPK7, a member of calcium-dependent protein kinases family as an unexpected negative regulator of the cellular abundance of a family of aquaporins (PIP1, Plasma membrane Intrinsic Protein 1). In addition, this study revealed that the cellular amount of a few additional membrane transporters is controlled by CPK7. Thus this work provides evidence for a new CPK7-dependent mechanism involved in the stability of specific membrane proteins, with effects on water transport and possibly other root functions, opening new perspectives in membrane protein research. © 2014 John Wiley & Sons Ltd. Source

Di Pietro M.,CNRS Biochemistry and Plant Molecular Physiology Laboratory | Vialaret J.,Laboratoire Of Proteomique Fonctionnelle | Vialaret J.,Montpellier University Hospital Center | Hem S.,CNRS Biochemistry and Plant Molecular Physiology Laboratory | And 5 more authors.
Molecular and Cellular Proteomics | Year: 2013

In plants, aquaporins play a crucial role in regulating root water transport in response to environmental and physiological cues. Controls achieved at the post-translational level are thought to be of critical importance for regulating aquaporin function. To investigate the general molecular mechanisms involved, we performed, using the model species Arabidopsis, a comprehensive proteomic analysis of root aquaporins in a large set of physiological contexts. We identified nine physiological treatments that modulate root hydraulics in time frames of minutes (NO and H2O2 treatments), hours (mannitol and NaCl treatments, exposure to darkness and reversal with sucrose, phosphate supply to phosphate-starved roots), or days (phosphate or nitrogen starvation). All treatments induced inhibition of root water transport except for sucrose supply to darkgrown plants and phosphate resupply to phosphatestarved plants, which had opposing effects. Using a robust label-free quantitative proteomic methodology, we identified 12 of 13 plasma membrane intrinsic protein (PIP) aquaporin isoforms, 4 of the 10 tonoplast intrinsic protein isoforms, and a diversity of post-translational modifications including phosphorylation, methylation, deamidation, and acetylation. A total of 55 aquaporin peptides displayed significant changes after treatments and enabled the identification of specific and as yet unknown patterns of response to stimuli. The data show that the regulation of PIP and tonoplast intrinsic protein abundance was involved in response to a few treatments (i.e. NaCl, NO, and nitrate starvation), whereas changes in the phosphorylation status of PIP aquaporins were positively correlated to changes in root hydraulic conductivity in the whole set of treatments. The identification of in vivo deamidated forms of aquaporins and their stimulus-induced changes in abundance may reflect a new mechanism of aquaporin regulation. The overall work provides deep insights into the in vivo post-translational events triggered by environmental constraints and their possible role in regulating plant water status. Molecular & Cellular Proteomics 12: 10.1074/mcp.M113.028241, 3886-3897, 2013. © 2013 by The American Society for Biochemistry and Molecular Biology, Inc. Source

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