Overexpression of PeHKT1;1 Improves Salt Tolerance in Populus

Abstract

Soil salinization is an increasingly serious threat that limits plant growth and development. Class I transporters of the high-affinity K⁺ transporter (HKT) family have been demonstrated to be involved in salt tolerance by contributing to Na⁺ exclusion from roots and shoots. Here, we isolated the <i>PeHKT1;1</i> gene from hybrid poplar based on the sequences of the <i>Populus trichocarpa</i> genome. The full-length <i>PeHKT1;1</i> gene was 2173 bp, including a 1608 bp open reading frame (ORF) encoding 535 amino acids and containing eight distinct transmembrane domains. Multiple sequence alignment and phylogenetic analysis suggested that the PeHKT1;1 protein had a typical S⁻G⁻G⁻G signature for the P-loop domains and belonged to class I of HKT transporters. <i>PeHKT1;1</i> transcripts were mainly detected in stem and root, and were remarkably induced by salt stress treatment. In further characterization of its functions, overexpression of <i>PeHKT1;1</i> in <i>Populus davidiana</i> × <i>Populus bolleana</i> resulted in a better relative growth rate in phenotypic analysis, including root and plant height, and exhibited higher catalase (CAT), peroxidase (POD), and superoxide dismutase (SOD) activities than non-transgenic poplar under salt stress conditions. These observations indicated that <i>PeHKT1;1</i> may enhance salt tolerance by improving the efficiency of antioxidant systems. Together, these data suggest that <i>PeHKT1;1</i> plays an important role in response to salt stress in <i>Populus</i>.