Abstract
MYB transcription factors constitute a diverse and functionally versatile family, playing central roles in regulating plant responses to a range of abiotic stressors. Based on previous research, we identified and characterized a maize MYB transcription factor gene, ZmMYBR24, which is involved in responses to salt, alkali, and low-temperature stress. This study aimed to investigate the function and mechanism of ZmMYBR24 in response to salt, alkali, and low-temperature stresses. We hypothesized that ZmMYBR24 regulates biosynthetic pathways to influence maize resistance to multiple abiotic stresses. The results indicate that ZmMYBR24 expression was markedly upregulated (p < 0.01) and the fold-change in gene expression ranged from 1.54 to 25.69 when plants were exposed to these combined stresses. Phenotypically, the zmmybr24 mutant line exhibited more pronounced inhibition of seedling and root growth under stress compared to the wild-type B73 line. Based on a correlation expression pattern analysis and mutant line evaluation, ZmMYBR24 was confirmed to be a positive regulatory transcription factor for multiple types of abiotic stress resistance. An RNA-seq analysis of both lines revealed differentially expressed genes (DEGs), with gene ontology (GO) and KEGG enrichment analyses indicating that ZmMYBR24 may mediate stress responses by modulating the expression of genes involved in flavonoid biosynthesis. Notable differences were observed in the expression of pathway-associated genes between the mutant and wild-type plants. A haplotype analysis across 80 inbred maize lines revealed 16 ZmMYBR24 coding region haplotypes-comprising 25 SNPs and 17 InDels-with HAP12 emerging as a superior haplotype. These results demonstrate that ZmMYBR24 enhances maize yields by regulating the flavonoid biosynthesis pathway in response to adverse climatic conditions including salt, alkaline conditions, and low temperatures. Collectively, these findings offer novel insights into the molecular mechanisms underlying maize adaptation to combined abiotic stresses and lay the groundwork for breeding programs targeting multi-stress resistance.