Identification and Expression Analysis of Rice MYB Family Members in Response to Heat Stress

With the continuous rise in global temperatures, heat stress has become a significant threat to rice (Oryza sativa L.) growth and yield. MYB transcription factors, the largest family of genes in plants, play a crucial role in mediating responses to various abiotic stresses. However, the specific functions of MYB genes in rice under heat stress remain largely unexplored. In this study, we conducted a comprehensive genome-wide characterization of the MYB transcription factor family and performed an RNA-seq analysis to identify OsMYB genes that are responsive to heat stress. We identified 229 MYB genes in rice, 134 of which exhibited significant expression changes under heat treatment. An RT-qPCR analysis validated the RNA-seq results for 15 MYB genes, confirming significant expression changes, such as the upregulation of Os02g0685200 after heat stress and the downregulation of Os05g0579600. Six highly responsive genes were selected for further analysis. Cis-acting elements associated with hormone response and abiotic stress were identified in the promoter regions of these genes. A subcellular localization analysis revealed that, except for Os05g0579600, which located to both the nucleus and cytoplasm, the other MYB genes (Os01g0192300, Os02g0685200, Os06g0637500, Os06g0669700, and Os09g0106700) were predominantly located in the nucleus. In yeast, Os01g0192300, Os06g0637500, and Os06g0669700 exhibited transcriptional activation activity, while Os02g0685200 and Os09g0106700 showed transcriptional repression activity. Notably, these genes responded not only to heat stress but also to other abiotic stresses, such as cold, salt, and heavy metal cadmium. This study provides valuable insights into the functional roles of OsMYB family genes in the heat stress response, identifying Os01g0192300, Os02g0685200, Os05g0579600, Os06g0637500, Os06g0669700, and Os09g0106700 as potential key genes involved in heat tolerance in rice.