Screening and Identification of Cinnamoyl CoA Reductase Genes Associated with Lignin Synthesis and Abiotic Stress in Boehmeria nivea

Ramie (Boehmeria nivea (L.) Gaudich.) is a bast fiber crop that can be used in textiles, medicine, and feed and for environmental protection. Lignin plays an important role in plant defense and development, but lignin is a critical factor affecting the fiber and feed quality of ramie. Cinnamoyl-CoA reductase (CCR) is a pivotal enzyme in plant lignin biosynthesis that catalyzes the synthesis of these common precursors. Here, eight CCR genes of ramie were identified based on sequence characteristics, gene structure, phylogenetic relationships, stress response to abiotic treatment, and the correlation of lignin and flavonoid contents with the expression level of genes. The eight CCR genes were cloned and divided into three groups with significant differences in their structures and sequence characteristics. BnCCR1 and BnCCR5 are involved in lignin biosynthesis. BnCCR4 plays a role in defense-related processes. It is worth noting that BnCCR2 is different from the structure and function of typical CCR, which is closely related to the synthesis of both lignin and flavonoids, and may play different roles in the xylem and phloem of ramie. The functions of the other genes require further investigation. These findings provide a basis for subsequent functional verification of CCR genes using genetic engineering.