Mining of genes and pathways associated with long-term heat stress in Brassica juncea floral buds

This study integrated phenotypic and transcriptomic analysis of early (TS1) and late (TS2) floral buds stages to elucidate long-term heat stress (14 DAS) responses. Heat exposure reduced pollen viability (23.14%), pollen tube growth (19.20%), and stigma receptivity, along with abnormal bud swelling and anther desiccation. Transcriptome analysis revealed consistent repression of photosynthesis-related pathways while stress-responsive pathways exhibited stage-specific activation. Early-stage buds activated glutathione metabolism and ER protein processing, whereas late-stage buds enhanced α-linolenic acid and glycerolipid metabolism, indicating a temporal shift from cytoprotection to membrane remodeling. WGCNA analysis identified key-genes, including regulators of proteostasis (PUX5), lipid remodeling (KCS, HPL, GPAT, CER1), and redox-homeostasis (GSTF9) with ERF012, MYB-AS1, MYB106, GATA17 TFs as candidate central regulatory hubs for these pathways. Despite activation of protective pathways, substantial suppression of tapetum development, microsporogenesis, and anther dehiscence genes particularly in early-stage buds, explaining reproductive failure. These findings provide candidate targets for developing thermotolerance in Brassica crops.