PcCLCg is involved in the accumulation of Cl- in shoots for osmotic adjustment and salinity resistance in the Cl--tolerant xerophyte Pugionium cornutum

Purpose The xerophyte Pugionium cornutum is a salt-tolerant species that can accumulate high amounts of Cl- in shoots for osmotic adjustment under saline condition. However, the molecular basis underlying how P. cornutum uses Cl- as a beneficial osmoticum is not clear yet. In this study, we evaluated the function of a chloride channel PcCLCg from P. cornutum in vacuolar Cl- compartmentalization and plant salt tolerance. Methods PcCLCg was cloned; its subcellular localization and expression patterns were analyzed; its function in vacuolar Cl- compartmentalization, ion homeostasis and plant salt tolerance were investigated by expression in yeast and Arabidopsis. Results PcCLCg was located on the tonoplast, the encoding gene was mainly expressed in shoots, and the expression level was induced by Cl--salts. The expression of PcCLCg could improve the growth and increase the Cl- content of the yeast mutant Delta gef1, in which a chloride channel gene ScGEF1 is deleted, under Cl--salt treatments. The overexpression of PcCLCg in wild-type Arabidopsis or atclcg mutant alleviated the detrimental effects of NaCl stress on plant growth and significantly increased shoot Cl- and Na+ content under NaCl treatments. Interestingly, PcCLCg-overexpressing lines showed an increased expression of SLAH1 and NHX1 in roots and shoots, respectively, while a decreased expression of SOS1 in roots than wild-type under salt stress. Conclusions The upregulated expression of PcCLCg in shoots is conducive to vacuolar Cl- compartmentalization and regulation of Na+ and Cl- accumulation, thus enhancing the osmotic adjustment capacity in the shoot of P. cornutum under saline conditions.