A bamboo bHLH transcription factor PeRHL4 has dual functions in enhancing drought and phosphorus starvation tolerance.

ROOTHAIRLESS (RHL) is a typical type of basic helix-loop-helix (bHLH) transcription factor (TF), which has been reported to participate in various aspects of plant growth and in response to stress. However, the functions of RHL subfamily members in moso bamboo (Phyllostachys edulis) remain unknown. In this study, we identified 14 bHLH genes (PeRHL1-PeRHL14) in moso bamboo. Phylogenetic tree and conserved motif analyses showed that PeRHLs were clustered into three clades. The expression analysis suggested that PeRHL4 was co-expressed with PeTIP1-1 and PePHT1-1 in moso bamboo. Moreover, these three genes were all up-regulated in moso bamboo under drought stress and phosphate starvation. Y1H, DLR and EMSA assays demonstrated that PeRHL4 could activate the expression of PeTIP1-1 and PePHT1-1. Furthermore, overexpression of PeRHL4 could increase both drought and phosphate starvation tolerance in transgenic rice, in which the expression of OsTIPs and OsPHT1s was significantly improved, respectively. Overall, our results indicated that drought stress and phosphate starvation could induce the expression of PeRHL4, which in turn activated downstream genes involved in water and phosphate transport. Collectively, our findings reveal that PeRHL4 acting as a positive regulator contributes to enhancing the tolerance of moso bamboo under drought stress and phosphate starvation.