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.

Rice (Oryza sativa L.), a fundamental global staple, nourishes over half of the world’s population. The identification of the ddt1 mutant in rice through EMS mutagenesis of the indica cultivar Shuhui527 revealed a dwarf phenotype, characterized by reduced plant height, smaller grain size, and decreased grain weight. Detailed phenotypic analysis and map-based cloning pinpointed the mutation to a single-base transversion in the LOC_Os03g04680 gene, encoding a cytochrome P450 enzyme, which results in a premature termination of the protein. Functional complementation tests confirmed LOC_Os03g04680 as the DDT1 gene responsible for the observed phenotype. We further demonstrated that the ddt1 mutation leads to significant alterations in gibberellic acid (GA) metabolism and signal transduction, evidenced by the differential expression of key GA-related genes such as OsGA20OX2, OsGA20OX3, and SLR1. The mutant also displayed enhanced drought tolerance, as indicated by higher survival rates, reduced water loss, and rapid stomatal closure under drought conditions. This increased drought resistance was linked to the mutant’s improved antioxidant capacity, with elevated activities of antioxidant enzymes and higher expression levels of related genes. Our findings suggest that DDT1 plays a crucial role in regulating both plant height and drought stress responses. The potential for using gene editing of DDT1 to mitigate the dwarf phenotype while retaining improved drought resistance offers promising avenues for rice improvement.

Leaf senescence is a crucial trait that significantly impacts crop quality and yield. However, whether plant leaf senescence genes are regulated by the same mechanisms in vitro and in vivo has not been determined. Here, we screened a rice (Oryza sativa) leaf senescence mutant exhibiting a delayed leaf senescence phenotype in vitro and an early leaf senescence phenotype in vivo. Map-based cloning revealed that these phenotypes were caused by OsELS6, which encodes ABERRANT LATERAL ROOT FORMATION4 (ALF4), a protein that inhibits SKP1-CUL1-F box protein (SCF) E3 ligase activity. In addition, OsELS6 interacted with the U-box E3 ligase OsHUB1, which may be involved in seed development, and with OsCDC48, which is involved in leaf senescence. Integrated transcriptomic, proteomic, and ubiquitomic analyses, as well as exogenous application of jasmonic acid (JA) , demonstrated that OsELS6 is related to OsCDC48 and plays opposite roles in rice leaf senescence in vitro and in vivo via the JA pathway. This study elucidated the regulatory mechanisms of OsELS6 in rice leaf senescence in vitro and in vivo, revealing that JA plays a key role in the regulation of leaf senescence by OsELS6 and OsCDC48.

Heat stress (HS) severely threatens rice (Oryza sativa) growth, development, and yield formation; elucidating regulatory mechanisms underlying rice thermotolerance is essential. Here, we dissected the role of OsMYBR17, a previously uncharacterized R2R3-MYB transcription factor, in the heat-stress responses of rice using gain- and loss-of-function approaches combined with DNA affinity purification sequencing (DAP-seq) and RNA sequencing (RNA-seq). The results indicated that OsMYBR17 was induced by HS. Overexpression of OsMYBR17 markedly enhanced seedling thermotolerance, whereas CRISPR/Cas9-mediated knockout lines exhibited pronounced heat hypersensitivity. OsMYBR17-overexpression plants accumulated less reactive oxygen species and exhibited reduced lipid peroxidation, as reflected by lower malondialdehyde levels, accompanied by elevated ascorbate peroxidase activity. Consistently, chloroplast structural integrity and chlorophyll-associated signals were better maintained in overexpression lines under prolonged heat exposure, while opposite trends were observed in knockout mutants. Integrative analysis of DAP-seq and RNA-seq identified multiple heat- and oxidative stress-associated candidate targets regulated by OsMYBR17, among which OsLEA4 emerged as a prominent target. Further analyses demonstrated that OsMYBR17 recognized specific cis-elements in the OsLEA4 promoter and directly activated its transcription. Functional analysis of OsLEA4 gain- and loss-of-function materials, together with genetic analysis in the OsMYBR17-overexpression background, further supported its positive contribution to thermotolerance. Collectively, our findings establish an OsMYBR17–OsLEA4 regulatory module that enhances rice heat tolerance and is associated with improved redox homeostasis and chloroplast stability under HS. This study advances our understanding of the molecular basis of heat-stress tolerance in rice and highlights OsMYBR17 and OsLEA4 as potential targets for developing heat-resilient rice cultivars.