Genome-wide identification, Characterization, and Expression analysis of the Caffeic Acid O-Methyl Transferase (COMT) Gene Family of Sorghum Bicolor

Caffeic acid O-methyltransferases (COMTs) are essential enzymes for producing natural products in plants, specifically involved in the phenylalanine metabolic pathway and the monolignol biosynthetic pathway. These enzymes are responsible for the methylation of caffeic acid compounds, which are the building blocks for many plant-derived compounds with various biological activities. The investigation of the evolutionary divergence, expression patterns under diverse abiotic stress conditions, and lignin content-related features of the COMT gene family in Sorghum has not been explored. In this study, forty-eight SbCOMTs were identified in S.bicolor. Based on the examination of evolutionary relationships, 48 SbCOMTs were classified into two distinct categories. The gene characterization and the conserved motif patterns in each group were similar, demonstrating the reliability of the phylogenetic categorization. Chromosomes 5 and 7 have been found as the hotspot of SbCOMTs with 10 and 7 genes respectively. Phylogenetic analysis revealed the conservation of Sorghum COMT genes among Zea mays and Oryza sativa. Investigation of regulatory elements specifies the significant roles that COMT genes play in the monolignol biosynthetic pathway of S. bicolor. Analysis of miRNA, transcription factor binding, and gene expression analysis provides insights to further engineer lignin biosynthetic pathway for better biofuel yield. We found that two SbCOMTs (SbCOMT26& 36) were highly expressed and their relative contents were similar to the variation drift of lignin content under abiotic stress conditions in S. bicolor. These results provide a clue for further study on the roles of SbCOMTs in the development of Sorghum and could favourably be foundations for the cultivation of Sorghum with higher biomass and yield with enhanced abiotic stress tolerance.