Comprehensive Analysis of IDD Transcription Factors and Their Expression Profiling Under Pathogen Stress in Wheat.

INDETERMINATE DOMAIN (IDD) transcription factors are plant-specific regulators essential for plant development and stress adaptation. As a globally important staple crop, common wheat (Triticum aestivum L.) is frequently threatened by fungal diseases such as powdery mildew and stripe rust. To date, however, the IDD gene family in wheat has not been systematically characterized, and its roles in biotic stress responses remain unclear. In this study, we performed genome-wide identification and a comprehensive analysis of the TaIDD gene family. A total of 41 TaIDD genes were identified, which were unevenly distributed across 15 chromosomes and divided into four phylogenetic groups. Synteny and selective pressure analyses demonstrated that segmental duplication was the main driver of family expansion and that TaIDD genes underwent strong purifying selection during evolution. Cis-acting element analysis revealed abundant hormone- and stress-related elements in their promoter regions. Transcriptome and RT-qPCR analyses indicated that TaIDD genes exhibited distinct expression patterns under abiotic and biotic stress. Notably, TaIDD13, TaIDD19, TaIDD27, TaIDD37, TaIDD39, and TaIDD41 were significantly induced by multiple fungal pathogens, suggesting their potential involvement in stress-responsive pathways that may be related to disease resistance. Subcellular localization analysis further confirmed that TaIDD39 was exclusively localized in the nucleus, consistent with its function as a transcriptional regulator. Our findings provide insights into the evolutionary characteristics and stress-response mechanisms of TaIDD genes and highlight TaIDD39 and other potential candidates that may serve as valuable resources for wheat molecular breeding to enhance broad-spectrum disease resistance and stress tolerance.