Transcriptomic Analysis Revealed the Response Mechanism of Green Revolution Gene Rht-D1b in Wheat to Salt Stress

The semi-dwarfing gene Rht-D1b (formerly known as Rht2) was introduced into modern wheat breeding during the Green Revolution to reduce plant height, improve lodging resistance, and increase harvest index. In this study, two wheat (Triticum aestivum L.) lines carrying Rht-D1b (dwarf) and Rht-D1a (tall), respectively, were used to assess the role of Rht-D1b in salt tolerance through physiological and transcriptomic analyses under salt stress. Compared with Rht-D1a, Rht-D1b showed less growth inhibition, with smaller decreases in plant height, root length, and shoot biomass, as well as higher SPAD values. Rht-D1b also accumulated less Na+, had lower ROS and MDA levels, and maintained stronger POD and CAT antioxidant enzyme activities. Transcriptome analysis showed that 20 POD genes were consistently upregulated in Rht-D1b to Rht-D1a at 0, 6, and 24 h, while ion-transport- and ROS-related genes showed time-specific activation patterns linked to Na+ homeostasis, calcium signaling, and antioxidant defense. Together, these findings suggest that Rht-D1b may contribute to wheat seedling salt tolerance by improving ion homeostasis and redox balance. The salt-responsive genes identified in this study may also serve as candidates for future functional studies and wheat breeding.