Genome-wide identification and expression profiling of TaECI and TaDCI gene families suggest their potential involvement in wheat response to heat and osmotic stress

High temperature and drought are the predominant abiotic stresses that severely limit wheat ( Triticum aestivum L.) yield and productivity worldwide. Peroxisomal β-oxidation is a core metabolic pathway responsible for fatty acid catabolism and energy replenishment, and it critically regulates plant adaptation and tolerance to unfavorable environmental conditions. Δ³,Δ²-enoyl-CoA isomerase ( ECI ) and Δ³,⁵,Δ²,⁴-dienoyl-CoA isomerase ( DCI ) act as essential auxiliary enzymes that mediate the β-oxidation of unsaturated fatty acids. However, the evolutionary characteristics and stress-responsive transcriptional profiles of TaECI and TaDCI gene families remain poorly understood in wheat, restricting the elucidation of their roles in stress tolerance. In the present study, we systematically characterized the TaECI and TaDCI gene families at the genome-wide level in hexaploid wheat (cv. Chinese Spring). A total of 13 TaECI and 5 TaDCI family members were identified. Phylogenetic analysis, gene structure annotation and conserved motif detection demonstrated high sequence and structural conservation within the TaECI and TaDCI subfamilies, suggesting potential functional conservation among these genes in wheat. Promoter cis-element analysis revealed numerous cis-regulatory elements associated with phytohormone signaling and abiotic stress responses, suggesting that TaECI and TaDCI genes are extensively modulated by multiple environmental and hormonal signals. Quantitative real-time PCR (qRT-PCR) assays further verified their differential expression patterns under PEG-simulated osmotic stress and heat stress. PEG-simulated osmotic stress significantly upregulated TaECI4-D (3.2-fold induction, FDR-adjusted P < 0.01) and TaECI4-A (2.1-fold induction, FDR-adjusted P < 0.05). Under high-temperature stress, TaECI4-B , TaECI4-A , TaDCI1-D and TaDCI1-A were significantly upregulated at the transcriptional level. Notably, qRT-PCR validation showed that TaECI4-D was significantly upregulated under PEG-simulated osmotic stress, while TaECI4-B , TaDCI1-D and TaDCI1-A were significantly upregulated under heat stress. Only TaECI4-A showed positive transcriptional responses to both PEG-simulated osmotic stress and heat stresses, serving as a dual-stress responsive gene. Protein-protein interaction network prediction further indicated potential functional coordination between TaECI and TaDCI proteins, which may synergistically promote peroxisomal fatty acid degradation and thereby enhance wheat stress tolerance. This study comprehensively clarifies the evolutionary features, structural characteristics and divergent stress-responsive expression patterns of the TaECI and TaDCI gene families in wheat. TaECI4-A , whose induction under both stresses was independently confirmed by qRT-PCR, represents a promising candidate for further functional characterization of wheat responses to multiple abiotic stresses.