Trihelix gene identification and functional analysis of HvTH1 regulator's role in ROS detoxification during salt stress conditions in wild barley.

Salt stress inhibits the growth and productivity of the important cereal crop barley. To overcome this challenge, we studied a genome-wide and functional analysis of the trihelix genes. They showed diverse functions involved in hormone, light, and stress responses, with multiple evolutionary events and gene duplications inferred. The candidate HvTH1 was highly expressed under salt stress. In the current study, the barley strip mosaic virus (BSMV) gene knockdown technique was implemented to characterize the functional role of HvTH1 in salt stress adaptation. Further morphological, physiological, and biochemical evidence has supported HvTH1 in salt stress adaptation. All parameters of root morphology were significantly affected by salt treatment in HvTH1 knockdown plants, including root number, root tips, root length, root diameter, root volume, and root surface area, indicating that the root system plays an adaptive role. A decline in the chlorophyll SPAD value and stomatal conductance in the HvTH1 knockdown plants after the salt treatment indicates stomatal malfunction and consequently impairs CO₂ assimilation. Moreover, histochemical staining and the measurement of O₂⁻ and H₂O₂ showed that salt stress enhanced these compounds in the knockdown lines of HvTH1, further confirming the role of the gene in regulating ROS, as evidenced by the higher MDA levels presumably stimulated by a higher production rate of ROS. Furthermore, SOD, CAT, and APX antioxidant activities had declined in HvTH1 knockdown lines, and this might enhance the oxidative stress. Thus, HvTH1 is crucial in managing ROS levels, antioxidant activities, and the salt stress response in barley.