Unraveling of the main physiological processes affected by the Na+, K+ transporters NHX1 and NHX2 of Arabidopsis thaliana
The Arabidopsis thaliana NHX1 and NHX2 are the two major tonoplast-localized isoforms of Na+,K+/H+ antiporters. NHX1 and NHX2 have similar expression patterns and identical biochemical activity, and together they account for a significant amount of the Na+,K+/H+ antiport activity in tonoplast vesicles. Double mutants nhx1 nhx2 have reduced ability to create the vacuolar K+ pool, show high K+ retention in the cytosol, impaired osmoregulation, and compromised turgor generation for cell expansion. Moreover NHX1 and NHX2 exchangers are pivotal in the vacuolar accumulation of K+ of guard cells as the nhx1 nhx2 mutant lines are dysfunctional in stomatal regulation, showing impaired stomatal opening and closure due to the abrogation of K+ accumulation in the guard cells. Other phenotypic traits of the double mutant are poor growth, hypersensitivity to osmotic stress and very low fertility. Some of these phenotypic traits can be suppressed by the addition of moderate amounts of NaCl in the substrate. To determine what is the precise physiological function critically affected by nhx1 nhx2 that accounts for most of the mutant phenotype, we have analyzed the root and aerial part functions of NHX proteins by reciprocal micrografting of wild-type and mutant roots and shoots, and by guard cell specific expression of NHX1 and NHX2 proteins in a double mutant genetic background. We have evaluated the growth, fertility and stomatal function of these chimaeric plants. The results indicate that defective osmotic regulation is the main cause of the pleiotropic phenotype of mutants impaired in NHX function.
| Main Authors: | , , , |
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| Format: | póster de congreso biblioteca |
| Published: |
Universidad de Oviedo
2016-06-22
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| Online Access: | http://hdl.handle.net/10261/160442 |
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