Transcriptional reprogramming of heat-sensitive maize anther development under heat stress

Heat stress during anther development severely impairs pollen fertility and substantially reduces yield. However, how heat stress reshapes transcriptional programs at specific anther developmental stages and which regulatory mechanisms underlie stage-dependent sensitivity remain unclear. Here, we employed the heat-sensitive maize inbred line Zheng641 as experimental material, established control and heat-stress treatments through staggered sowing, and sampled anthers at distinct developmental stages based on anther length to systematically characterize the fine-scale transcriptional responses to heat stress. Morphological analyses showed that elevated temperatures markedly reduced tassel branch number and pollen viability and delayed tapetal degradation. High-resolution transcriptomic profiling revealed that heat stress mainly activated the pathways related to fatty acid biosynthesis and carbohydrate metabolism during the early stage of pollen development, whereas late-stage heat stress induced amino acid transport and biosynthesis while repressing cell wall modification and protein folding. Phase-specific transcription factor analysis indicated that bHLH transcription factors were significantly enriched before the tetrad stage, AP2/ERFs in microspore stage, MYBs in pollen mature stage. Furthermore, we explored ZmAGP2 could improve thermotolerance by the phenotypic analysis of transgenic overexpressed lines. Notably, loss-of-function of ZmAGP2 significantly reduced pollen viability and seed set under heat stress. Together, these findings provide a high-resolution transcriptomic framework for understanding the molecular basis of maize anther sensitivity to heat and identify promising targets for enhancing thermotolerance in maize breeding.