Maize ZmBES1/BZR1-7 Transcription Factor Positively Regulates Drought Tolerance in Transgenic Arabidopsis and Rice

Drought stress significantly limits agricultural productivity and threatens food security. The identification of drought tolerance genes and the dissection of their regulatory networks in crops are crucial for ensuring future food production. The BRI1-EMS1 suppressor (BES1)/brassinazole-resistant 1 (BZR1) family is a kind of plant-specific transcription factor that regulates growth, development, and stress responses in plants. Here, the maize ZmBES1/BZR1-7 gene was cloned and transformed into Arabidopsis and rice to characterize plant phenotypes under drought stress conditions. Sequence analysis revealed that the ZmBES1/BZR1-7 protein contains a conserved basic helix-loop-helix (bHLH) domain, localizes to the nucleus, and exhibits transcriptional activation activity. Expression profiling revealed that ZmBES1/BZR1-7 is induced by drought stress in maize. Overexpression of ZmBES1/BZR1-7 significantly enhanced drought tolerance in both transgenic Arabidopsis and rice. Under drought stress conditions, all transgenic lines showed higher survival rates and relative water content (RWC), increased root length, reduced relative electrolyte leakage (REL) and malondialdehyde (MDA) content, as well as higher yield of transgenic rice than the wild type. Integrated analyses of RNA-seq and qRT-PCR assays demonstrated that ZmBES1/BZR1-7 modulates transcription of stress-responsive genes to enhance drought tolerance. Collectively, the study provides insights into the molecular mechanisms by which ZmBES1/BZR1-7 mediated drought stress response in maize.