The / Module Mediates Lateral Root Growth under Salt Stress via the Auxin Pathway.

Salt-induced developmental plasticity in a plant root system strongly depends on auxin signaling. However, the molecular events underlying this process are poorly understood. (), s (s), and () form a regulatory module involved in controlling lateral root (LR) growth. Here, we found that expression was strongly induced by exposure to salt during LR formation in poplar ( spp.) plants. overexpression stimulated LR development and increased salt tolerance, whereas knockdown caused by a short tandem target mimic repressed LR growth and compromised salt resistance. , , and expression was inhibited significantly by the presence of salt, and transcript abundance was decreased dramatically in the -overexpressing line but increased in the -knockdown line. Constitutive expression of harboring mutated -binding sites removed the salt resistance of the overexpressors. positively regulated auxin signaling in LRs subjected to salt, but inhibited auxin signaling. Salinity stabilized the poplar Aux/IAA repressor INDOLE-3-ACETIC ACID17.1, and overexpression of an auxin/salt-resistant form of this repressor suppressed LR growth in -overexpressing and -RNA interfering lines in the presence of salt. Thus, the module is a key regulator, via modulating the auxin pathway, of LR growth in poplar subjected to salt stress.