Wheat TaAP2/ERF Genes Regulate Heat Tolerance Through Ethylene Signaling at Grain-Filling Stage

Wheat is a globally important crop, and its production is critically challenged by heat stress. To understand the heat tolerance mechanism at grain-filling stage in wheat, two genotypes, W156 (tolerant) and Brazil 32 (susceptible) were evaluated for their morphological responses and expressions of TaAP2/ERF super-family transcription factor genes under heat stress (at 37/27 °C) at 11 days and 13 days post-anthesis. The W156 showed significantly higher thousand kernel weight (TKW), chlorophyll fluorescence (Fv/Fm) and delayed senescence of flag leaf and exposed peduncle. Twenty-two differentially expressed genes (DEGs) were selected from in silico expression analysis of 630 TaAP2/ERF genes under abiotic stress and their RT-qPCR expression validation identified twenty major DEGs responsive to heat stress. Co-expression network analysis of these DEGs identified hub TF genes including TraesCS1A02G221900, TraesCS6D02G324200, TraesCS6B02G331000, TraesCS4D02G298600, TraesCS5B02G193200, and TraesCS1A02G058400. Gene Ontology analysis and Gene Set Enrichment Analysis further revealed that 16 (80