Genome-wide identification, characterization and expression analysis of the CesA/Csl superfamily in Boehmeria nivea and its feral species

The cellulose synthase (CesA) and cellulose synthase-like (Csl) superfamily functions as the core enzymatic system for plant cell wall biosynthesis and is pivotal for bast fiber development. Boehmeria nivea (ramie) is a economically vital bast fiber crop, yet systematic analysis of its CesA/Csl superfamily remains lacking. In this study, a total of 9 CesA and 22 Csl genes was identified in cultivated ramie B. nivea and 7 CesA and 20 Csl genes in feral ramie B. nivea var. tenacissima . Phylogenetic analysis clustered these genes into one CesA subfamily and six Csl subfamilies, with CesA genes further divided into primary cell wall and secondary cell wall subgroups. Chromosomal localization showed scattered distribution and tandem duplication events. Syntenic analysis revealed high conservation of CesA/Csl loci between the two varieties, although a CesA8 , CesA10 and several Csl orthologs were not detected in the current feral genome assembly. Promoter analysis identified abundant light-, phytohormone-, and MYB-responsive cis -elements. Expression profiling demonstrated high expression of BnCesA4/7/8 in stems and middle bark tissues, where bast fibers underwent active tertiary cell wall thickening, suggesting their potential involvement in tertiary cell wall biosynthesis during fiber development. Protein structural modeling verified that BnCesA4 contained conserved catalytic residues and formed a canonical homotrimeric complex. This study revealed evolutionary conservation and expression divergence of the CesA/Csl superfamily in ramie, and identified BnCesA4/7/8 as potential key candidate genes regulating G-layer cellulose biosynthesis. These results established a foundational genomic resource for further functional studies of fiber development and cell wall biosynthesis in ramie.