Genes encoding ion transporters that regulate ion homeostasis in soybean have not been carefully investigated. Using degenerate primers, we cloned a putative chloride channel gene ( GmCLC1 ) and a putative Na + /H + antiporter gene ( GmNHX1 ) from soybean. Confocal microscopic studies using yellow fluorescent fusion proteins revealed that GmCLC1 and GmNHX1 were both localized on tonoplast. The expressions of GmCLC1 and GmNHX1 were both induced by NaCl or dehydration stress imposed by polyethylene glycol (PEG). Using mitochondrial integrity and cell death as the damage indicators, a clear alleviation under NaCl stress (but not PEG stress) was observed in both GmCLC1 and GmNHX1 transgenic cells. Using fluorescent dye staining and quenching, respectively, a higher concentration of chloride ion (Cl -) or sodium ion (Na + ) was observed in isolated vacuoles in the cells of GmCLC1 and of GmNHX1 transgenic lines. Our result suggested that these vacuolar-located ion transporters function to sequester ions from cytoplasm into vacuole to reduce its toxic effects.
Summary• G-proteins (guanine nucleotide-binding proteins that usually exhibit GTPase activities) and related signal transduction processes play important roles in mediating plant defense responses; here, a rice (Oryza sativa) cDNA clone, OsGAP1, encoding a GTPase-activating protein (GAP) that also contains a protein kinase C conserved region 2 (C2) domain is reported.• An interacting G-protein partner for the OsGAP1 protein was identified by yeast two-hybrid library screening and confirmed by co-immunoprecipitation; the GTPaseactivation activity of OsGAP1 on this interacting G-protein was demonstrated using in vitro assays.• OsGAP1 was induced by wounding in rice and the presence of the R locus Xa14 enhances such induction.• Gain-of-function tests in transgenic rice and Arabidopsis thaliana showed that constitutive expression of OsGAP1 led to increased resistance to bacterial pathogens in both monocots and dicots.
Summary• The primary biochemical reaction of purple acid phosphatases (PAP) is to catalyze the hydrolysis of phosphate esters and anhydrides. However, the soybean GmPAP3 gene expression is induced by NaCl, osmotic, and oxidative treatments, indicating a possible role of PAP in abiotic stress responses.• Confocal and electron microscopic studies demonstrated that GmPAP3 protein is mainly localized in mitochondria, a primary site for reactive oxygen species (ROS) production.• When subjected to NaCl and polyethylene glycol (PEG) treatments, ectopic expression of GmPAP3 in transgenic tobacco BY-2 cells mimicked the protective effects exhibited by the antioxidant ascorbic acid: increase in the percentage of cells with active mitochondria; reduction in the percentage of dead cells; and reduced accumulation of ROS. In addition, when GmPAP3 transgenic Arabidopsis thaliana seedlings were subjected to NaCl, PEG, and paraquat (PQ) treatments, the percentage of root elongation was significantly higher than the wild type. Furthermore, PQinduced lipid peroxidation in these transgenic seedlings was also reduced.• In summary, the mitochondrial localized GmPAP3 may play a role in stress tolerance by enhancing ROS scavenging.
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