ZmMYB56 regulates stomatal closure and drought tolerance in maize seedlings through the transcriptional regulation of ZmTOM7

The growth and yield of essential crops, including maize, are significantly endangered by drought. Closing stomata, limiting water dissipation, and improving water use efficiency are important components of plant drought responses. In our study, the MYB-like transcription factor ZmMYB56, expressed in maize guard cells, played important roles in regulating stomatal closure and drought tolerance. Mutations in ZmMYB56 triggered elevated stomatal conductance, rapid water loss in isolated leaves, and severe drought sensitivity in plants. ZmMYB56 possesses transcriptional activation activity, and is expressed specifically in stomatal guard cells. As an R2R3 transcription factor, ZmMYB56 can bind the cis-acting element on the ZmTOM7 promoter sequence, activating its expression. Correspondingly, the ZmTOM7 transcript level is downregulated in Zmmyb56 seedlings. Transgenic Arabidopsis plants overexpressing ZmTOM7 exhibit limited stomatal conductance and elevated drought tolerance, while the ZmTOM7 mutation is linked to higher stomatal conductance and substantial drought sensitivity in maize seedlings. According to these findings, we conclude that ZmTOM7 operates as a key target gene of ZmMYB56 and is involved in ZmMYB56-regulated stomatal closure and maize drought tolerance. Our findings regarding the functional mechanisms of maize ZmMYB56 transcription factors in stomatal closure and drought stress enable a potential genetic resource for improving the drought resistance of maize.