Na+/H+ antiporter (NHX1) positively enhances cadmium (Cd) resistance and decreases Cd accumulation in tobacco plants cultivated in Cd-containing soil

Abstract

Na+/H+ antiporter (NHX1) was reported to be induced by NaCl in plants and NaCl can alleviate the toxic effect in plants caused by cadmium (Cd). However, it is unknown whether the NHX1 gene is involved in Cd adaptation in plants. This study aimed to explore the relationship between Cd resistance and NHX1 in plants. SseNHX1 gene obtained by shuffling using SsNHX1 from Suaeda salsa and SeNHX1 from Salicornia europaea as sequence templates in our previous work, conferred higher salt tolerance to yeast than SsNHX1 and SeNHX1. The overexpression of SsNHX1, SeNHX1, or SseNHX1 genes in tobacco was performed to explore the relationship between Cd resistance and NHX1 gene expression in plants. The NHX1 inhibitor amiloride was also used to assess the relationship between Cd resistance and NHX1 in plants. Under Cd stress treatment, transgenic tobacco exhibited better growth status, increased chlorophyll content, improved photosynthesis capacity and enhanced content of Na+ and K+ compared to wildtype plants. Moreover, transgenic tobacco showed less ROS accumulation, reduced MDA production, and decreased Cd2+ accumulation compared to WT plants. More importantly, transgenic tobaccos overexpressing SseNHX1 gene showed a greater resistance to Cd stress and less Cd accumulation than the transgenic tobaccos overexpressing SsNHX1 or SeNHX1 genes. Cd resistance and Cd accumulation in transgenic tobacco plants was closely correlated with the expression of NHX1 gene.