Temporal transcriptome analysis identified GmMYB14 conferred the tolerance against sodic alkaline stress through activating phenylpropanoid metabolism.

Alkaline toxicity is an ever-increasing abiotic stress that frequently causes soybean chlorosis, resulting in severe growth retardation and yield loss in sodic saline soil. However, the tolerant mechanism of soybean to alkaline toxicity remains largely elusive. In this study, two contrasting genotypes were employed: JY93 displayed more acute chlorosis, greater reactive oxygen species (ROS) production and MDA content, along with weaker secretion of phenolic compounds and impaired Fe homeostasis under alkaline conditions, indicating a greater susceptibility to alkaline toxicity than JY99. Temporal transcriptome analysis revealed that phenylpropanoid metabolism might serve as a common adaptive response to mitigating ROS burst and improving Fe bioavailability under alkaline stress. Within this pathway, GmMYB14 was identified more forcefully induced in JY99 than in JY93 over the course of alkaline treatment. Overexpressing GmMYB14 markedly enhanced alkaline tolerance in Arabidopsis, such as greater root length, chlorophyll content, biomass than wild type. Further investigation demonstrated GmMYB14 facilitated greater Fe accumulation and translocation in shoot of transgenic plants under alkaline stress, potentially through modulating the expression of key genes in phenylpropanoid metabolism. Collectively, these findings suggest that GmMYB14 is a promising candidate to develop alkaline-tolerant crop varieties.