A Bamboo HD-Zip Transcription Factor PeHDZ72 Conferred Drought Tolerance by Promoting Sugar and Water Transport

Drought drastically affects plant growth, development and productivity. Plants respond to drought stress by enhancing sugar accumulation and water transport. Homeodomain-leucine zipper (HD-Zip) transcription factors (TFs) participate in various aspects of plant growth and stress response. However, the internal regulatory mechanism of HD-Zips in moso bamboo (Phyllostachys edulis) remains largely unknown. In this study, we identified an HD-Zip member, PeHDZ72, which was highly expressed in bamboo shoots and roots and was induced by drought. Furthermore, PeSTP_46019, PeSWEET_23178 and PeTIP4-3 were identified as downstream genes of PeHDZ72 in moso bamboo by DAP-seq. The expressions of these three genes were all induced by drought stress. Y1H, DLR and GUS activity assays demonstrated that PeHDZ72 could bind to three types of HD-motifs in the promoters of these three genes. Overexpression of PeHDZ72 led to a remarkable enhancement in drought tolerance in transgenic rice, with significantly improved soluble sugar and sucrose contents. Meanwhile, the expressions of OsSTPs, OsSWEETs and OsTIP were all upregulated in transgenic rice under drought stress. Overall, our results indicate that drought stress might induce the expression of PeHDZ72, which in turn activated downstream genes PeSTP_46019, PeSWEET_23178 and PeTIP4-3, contributing to the improvement of cellular osmotic potential in moso bamboo in response to drought stress.