Overexpression of CsRCI2Henhances salt tolerance inCamelina sativa(L.)

Although plant rare cold inducible 2 (RCI2), a homolog of yeastPMP3, has been considered to play important roles in responses to abiotic stress in plants, the functional role ofRCI2in salt-stress tolerance remains largely unknown for crop plants. In this study, we determined the function ofCsRCI2HfromCamelinaunder salt stress. Subcellular localization analysis of the yellow fluorescent protein (YFP)-CsRCI2Hfusion protein revealed thatCsRCI2Hlocalizes to the plasma membrane in tobacco leaves. Expression ofCsRCI2Hwas greatly increased in the presence of 150 mM NaCl. CsRCI2H compensated for the salt sensitivity of the yeast mutant increment pmp3lacking thePMP3gene. CsRCI2H-overexpressing transgenicCamelinashowed improved seed germination, root growth and fresh weight under high salt stress.CsRCI2H-overexpressing transgenicCamelinadisplayed lower accumulation of Na(+)in the roots and shoots but higher K(+)and Ca(2+)accumulation in the shoots than wild type plants under salt stress. Furthermore,CsRCI2H-overexpressingCamelinadisplayed higher stomatal conductance and lower malondialdehyde under salt stress. Transcript levels of ion-homeostasis related genes, such asCsSOS1, CsSOS3, andCsHKT1, were significantly increased in theCsRCI2H-overexpressing transgenic plants upon salt treatment. These results suggest that Na(+)and K(+)homeostasis can be controlled by the Na(+)and K(+)transport systems throughout theCsRCI2H-overexpressing transgenicCamelinaplant under salt-stress conditions. Collectively, these results indicate thatCsRCI2Hcontributes to salt tolerance inCamelinaduring seed germination and seedling growth by reducing Na(+)toxicity in the plant cells via regulation of ion homeostasis.