Molecular characterization and functional analysis of a cation-chloride cotransporter gene from trifoliate orange (Poncirus trifoliata L.)

Abstract

A cation-chloride cotransporter gene PtrCCC from trifoliate orange was identified, its ectopic expression confers salt tolerance in transgenic tobacco. Salinity is one of the most serious environmental stresses that limit crop growth. Cation-chloride cotransporters (CCCs) are membrane proteins that are involved in plant development and salt tolerance. Here we provide an insight into the molecular characterization and functional analysis of CCC-encoding gene (PtrCCC) from trifoliate orange (Poncirus trifoliata L.). The open-reading frame of PtrCCC is 2943 bp in length, which encodes a protein of 980 amino acids. Phylogenetic analysis revealed that PtrCCC is closely related to CCCs from its allied genera as well as woody perennials. Quantitative real-time PCR (qRT-PCR) analysis demonstrated that PtrCCC was expressed in all tested tissues, with higher expression level in root tip and leaf tip. Its expression was up-regulated in the leaves of trifoliate orange under the presence of KCl conditions. Ectopic expression of PtrCCC gene in tobacco exhibited an improvement in salt tolerance. The transgenic plants had higher dry biomass in the roots and shoots than that in wild type plants. Moreover, under KCl and NaCl + KCl stress conditions, the accumulation of shoot Cl− was remarkably decreased in the transgenic lines as compared with the wild type plants. Collectively, these results suggest that PtrCCC plays an important role in salt tolerance, which is partially attributed to its role in ions homeostasis.