Abstract
The BRI1-EMS suppressor 1 (BES1)/brassinazole-resistant 1 (BZR1) transcription factors, key components in the brassinosteroid signaling pathway, play pivotal roles in plant growth and development. However, the function of BES1/BZR1 in crops during stress response remains poorly understood. In the present study, we characterized ZmBES1/BZR1-5 from maize, which was localized to the nucleus and was responsive to abscisic acid (ABA), salt and drought stresses. Heterologous expression of ZmBES1/BZR1-5 in transgenic Arabidopsis resulted in decreased ABA sensitivity, facilitated shoot growth and root development, and enhanced salt and drought tolerance with lower malondialdehyde (MDA) content and relative electrolyte leakage (REL) under osmotic stress. The RNA sequencing (RNA-seq) analysis revealed that 84 common differentially expressed genes (DEGs) were regulated by ZmBES1/BZR1-5 in transgenic Arabidopsis. Subsequently, gene ontology and KEGG pathway enrichment analyses showed that the DEGs were enriched in response to stress, secondary metabolism and metabolic pathways. Furthermore, 30 DEGs were assigned to stress response and possessed 2–15 E-box elements in their promoters, which could be potentially recognized and bound by ZmBES1/BZR1-5. Taken together, our results reveal that the ZmBES1/BZR1-5 transcription factor positively regulates salt and drought tolerance by binding to E-box to induce the expression of downstream stress-related genes. Therefore, our study contributes to the better understanding of BES1/BZR1 function in the stress response of plants.
Highlights
Environmental stimuli significantly restrict plant growth, development and reproduction
We found that the ZmBES1/brassinazole-resistant 1 (BZR1)-5 decreased abscisic acid (ABA) sensitivity and enhanced tolerance to osmotic stress in transgenic Arabidopsis
The results of quantitative real time PCR (qRT-PCR) showed that the expression of ZmBES1/BZR1-5 in maize shoot was induced by NaCl treatment and reached a peak after 9 h of treatment (Figure 1A)
Summary
Environmental stimuli significantly restrict plant growth, development and reproduction. BES1 shares a high identity with BZR1 at the amino acid level (88%) and N-terminal domain (97%), and several family members have been identified, including BES1/BZR1 homologs 1–4 (BEH1–4) [18,19] These transcription factors show functional redundancy in the BR signaling transduction pathway and, have been renamed BES1/BZR1s [18,19,23]. BES1/BZR1s have been reported to regulate drought, heat and freezing stress response through regulating the expression of glutathione S-transferase 1 (GST1), RESPONSIVE TO DESICCATION 26 (RD26) and CBF genes, as well as interacting with RD26 and WRKY transcription factors [31,32,33,34,35] In addition to their crucial roles in abiotic stress, BES1/BZR1s function in response to biotic and nutrition stresses, such as immunity, autophagy, nitrogen and phosphorus starvation [36,37,38]. Our novel findings provide additional knowledge for better understanding the function of ZmBES1/BZR1s in maize
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