Expression of poplar sex-determining gene affects plant drought tolerance and the underlying molecular mechanism.

It is frequently observed that plant sexes differ in their response to environmental stress. Poplars are dioecious plants, and sex separation of poplars is triggered by the sex-limited expression of the poplar sex-determining gene FERR. In this study, we over-expressed FERR in a male poplar and knocked it out in a female poplar. The over-expression lines exhibited distinct morphological and physiological changes rendering the transformed plants more tolerant to drought stress. By contrast, no obvious change in drought tolerance was observed in the knockout lines. Transcriptome sequencing and molecular interaction analysis demonstrated that the effect of FERR on drought tolerance was conferred by competitive interaction with protein phosphatase 2C and SNF1-related protein kinase 2 (SnRK2). Under drought stress, an FERR-SnRK2s-ARR5 complex forms and activates the ABA signaling pathway. Our results provide direct evidence that the expression of the poplar sex-determining gene pleiotropically affects plant drought tolerance.