The brassinosteroid-responsive xyloglucan endotransglucosylase/hydrolase 19 (XTH19) and XTH23 genes are involved in lateral root development under salt stress in Arabidopsis

Lateral roots (LRs) are the main component of the root system architecture in Arabidopsis. The plasticity of LR development has an important role in improving plant survival in response to the external environment. Previous studies have revealed a number of genetic pathways that control plant growth in response to environmental stimuli. Here, we find that the xyloglucan endotransglucosylase 19 (XTH19) andXTH23genes are involved in LR development under salt stress. The density of LRs was decreased in thexth23single mutant, which was also more sensitive to salt than the wild type, and thexth19xth23double mutant exhibited additive downregulated LR initiation and salt sensitivity compared with the single mutant. On the contrary, constitutive overexpression ofXTH19orXTH23caused increased LR densities. Furthermore,XTH19andXTH23were induced by salt via the key brassinosteroid signaling pathway transcription factorBES1. In addition, we found that 35S::BES1increased salt tolerance and the phenotype ofxth19xth23& 35S::BES1was partially complementary to the wild-type level.In vivoandin vitroassays demonstrated thatBES1acts directly upstream of XTH19andXTH23to control their expression. Overall, our results revealed thatXTH19andXTH23are involved in LR development via theBES1-dependent pathway, and contribute to LR adaptation to salt.