Genome-wide identification and expression pattern analysis of the COBRA-like gene family of Triticum aestivum (L.) under drought and heat stresses

T. aestivum (Triticum aestivum) (L.), rich in protein, carbohydrates, and minerals, is one of the world’s most important cereal grain crops, serving as the staple food source for 30% of the human population, underscoring its critical role in global food security. However, adverse environmental conditions such as high temperature and drought can severely restrict its growth, making the improvement of abiotic stress tolerance in T. aestivum a key research priority. The COBRA-like (COBL) gene family is key to regulating plant cell wall formation and abiotic stress responses. So far, a systematic genome-wide identification and functional characterization of the COBL gene family in T. aestivum has not been fully elucidated. Therefore, studying the involvement of the COBL gene family in abiotic stress regulation in T. aestivum could be very informative in showing how this crop deals with such stressful conditions. In this study, 39 TaCOBL gene family members were identified in the genome of T. aestivum genome using a combined approach of the HMMER (E-value threshold of 1e-5) program and BLASTP (E-value threshold of 1e-5). Comprehensive analyses were performed on their physicochemical properties, phylogenetic relationships, gene structures, conserved motifs, duplication events, and cis-acting elements. Using MEGA7 software to construct a phylogenetic tree of the COBL gene family revealed that this family can be divided into two Groups (Group I and Group II), which exhibit significant differences in gene structure and conserved motif composition. Analysis of duplication events indicated that whole-genome duplication (WGD) served as the primary mechanism for the expansion of the TaCOBL family. Most of the TaCOBL duplication gene pairs have a Ka/Ks ratio less than 1, except for TaCOBL-5 A/TaCOBL6-D, indicating the presence of purifying selection. The 2 kb upstream promoter region of the TaCOBL family genes revealed an abundance of cis-regulatory elements associated with hormones, stress responses, light signaling, and growth/development. Expression profiling using RNA-seq data demonstrated that TaCOBL genes were significantly differentially expressed in roots, stems, leaves, spikes and grains. Notably, based on log2 fold-change cutoff, TaCOBL9-D, TaCOBL14-A and TaCOBL14-D might are candidates genes for wheat heat stress tolerance, and TaCOBL3-B, TaCOBL8-B, TaCOBL9-A and TaCOBL9-B for drought stress tolerance. Overall, this study provides a theoretical foundation for the further function characterization of the TaCOBL gene family and proposes potential candidate genes for breeding stress-resistant T. aestivum.