Comprehensive analysis of cinnamoyl-CoA reductase (CCR) gene family in wheat: implications for lignin biosynthesis and stress responses.

BACKGROUND: Lignin, the second most abundant terrestrial biopolymer, represents a significant renewable natural biomaterial. Cinnamoyl-CoA reductase (CCR) catalyzes the conversion of various hydroxycinnamoyl-CoA esters into their corresponding aldehydes, utilizing NADPH as a cofactor. CCR functions as a regulatory point that controls the overall carbon flux towards lignin and constitutes the initial committed step in the lignin biosynthesis pathway. Additionally, CCR plays a crucial role in plant development and in resistance to biotic and abiotic stresses. Bread wheat (Triticum aestivum L.), a hexaploid crop, serves as a staple food for much of the global population. However, the copy number variation and expression characteristics of wheat CCR genes remain to be elucidated. RESULTS: This study identified 115 unique members of the CCR gene family through a comprehensive search of the wheat genome database. Subsequent analyses included the physicochemical properties, chromosomal localizations, gene duplication events, and structures of these genes. Wheat CCRs were categorized into TaCCR and TaCCR-like genes based on phylogenetic comparison, sequence alignment, and protein three-dimensional structure analysis. Twenty TaCCR proteins, characterized by key amino acid residues at the protein catalytic and NADPH-binding sites, were identified as genuine TaCCRs, potentially playing significant roles in lignin biosynthesis. The expression patterns of these 20 TaCCR genes were investigated in various wheat tissues and seedlings subjected to biotic and abiotic stresses. These genes may significantly influence stem development and responses to heat, drought, salt, and pathogen stresses. Additionally, degradome data analysis suggested that the expression of TaCCR6D-1 was regulated by miRNAs. Virus-induced gene silencing experiments demonstrated the involvement of TaCCR5-5 and TaCCR6-1 in wheat lignin synthesis. CONCLUSIONS: This study presents the first comprehensive identification and analysis of wheat CCR genes. Our findings establish a foundation for further elucidation of TaCCR functions and offer a significant genetic resource for future wheat improvement efforts.