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The contribution of the SOS signaling pathway in the cell wall dynamics in Arabidopsis
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International audience. Excess of salt in soil affects plant development and physiological mechanism thus reducing plant biomass production. It causes loss of cellular water, which reduces cell turgor, and as a consequence on cell wall extensibility. Plant cell wall is mostly composed of polysaccharides including cellulose, hemicelluloses and pectin and small amount of proteins. Pectin maintains the hydration status of the cell wall. The salt overly sensitive (SOS) pathway regulates homeostasis under salt stress. It includes SOS1 which encodes a plasma membrane Na+/H+ antiporter which is upregulated in response to salt stress under the control of SOS2/SOS3 regulatory pathway. The aim of the study was to investigate the cell wall structure in response to salt stress in sos1 and sos3 Arabidopsis deficient mutants which display a salt hypersensitivity phenotype and to get particularly new insights in the function of pectin and pectin remodeling enzymes.Four-d-old seedlings were transferred onto salinity medium (0, 50 and 75 mM NaCl) for 7 days. Under control condition, the cell wall contained highly lower amount of galacturonic acid (GalUA) residues and higher level of rhamnose, galactose (Gal) and arabinose (Ara) in sos3 compared to the WT. A similar trend was observed in sos1 but less pronounced. Under salt stress, minor changes in cell wall composition was observed in the WT. But in the sos mutants, both Ara and Gal residues increased significantly while the GalUA content strongly decreased. Pectin methylesterase enzyme activity was higher in both mutants under control condition compared to the WT. But under salt stress, its activity decreased in both mutants and the WT but was still higher in the sos mutants.These data showed that the SOS proteins could contribute besides ion homeostasis, to the cell wall dynamics, by protecting it against excessive Na+.
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