Genome-wide Identification of the Laccase Gene Family in White Jute (Corchorus capsularis): Potential Targets for Lignin Engineering in Bast Fiber

Jute (Corchorus spp.) is an important industrial bast fibre crop valued for its lignocellulosic fibres, yet the molecular basis of fibre lignification remains unexplored. Laccase (EC 1.10.3.2) is a key enzyme catalysing the final steps of lignin polymerisation. A genome-wide analysis of white jute (Corchorus capsularis) identified 34 putative laccase genes (CcaLACs), phylogenetically grouped into six clades. Expression profiling revealed predominant expression in phloem tissue (17 genes), followed by leaf (9) and xylem/root tissues (4). Several CcaLACs showed progressive upregulation from early growth to harvest stages. Homology with Arabidopsis laccases highlighted candidate genes involved in lignification, which were further supported by transcriptomic and qRT-PCR analyses. Notably, key CcaLACs showed significantly reduced expression in dlpf, a low-lignin white jute mutant. CcaLAC expression was also responsive to abiotic stresses, including abscisic acid and copper. MicroRNA target prediction identified Ath-miR397a and Ath-miR397b as potential regulators of multiple CcaLACs. Structural and subcellular analyses revealed conserved motifs, transmembrane domains, and diverse cellular localization. Gene ontology analysis linked CcaLACs to lignin and phenylpropanoid biosynthesis. Among them, CcaLAC28 and CcaLAC32 emerged as strong candidates regulating phloem fibre lignification, providing promising targets for developing low-lignin jute varieties for industrial applications.