Parida, S.; Jha, D. K.; Kumari, K.; Pradhan, S.; Dey, N.; Majumder, S.

The industrial bast fibre crop jute (Corchorus sp.) is known for its long lignocellulosic multi-utility fibres. Information on jute fibre lignification is limited, and many enzymes in the jute lignin pathway are not well documented. One such enzyme is laccase (EC 1.10.3.2), involved in the final polymerization step of lignification. A whole-genome search of white jute (Corchorus capsularis) revealed 34 putative laccase (CcaLAC) genes. Phylogenetic analysis categorized these genes into six groups, with 17 predominantly expressed in phloem tissue, 9 in leaf, and 4 in xylem and roots. A steady increase in gene expression, from plantlets to crop harvest, was observed for several CcaLACs. Some were selected for further analysis based on homology with Arabidopsis lignin pathway-modifying laccases (AtLACs). Transcriptomics data confirmed their expression in phloem tissues, with some showing significantly lower expression in dlpf, a low-lignin fibre-containing white jute mutant. Changes in CcaLAC expression were observed under abiotic stresses like ABA hormone and copper heavy metal. Target sites for Ath-miR397a and Ath-miR397b were predicted in 11 and 9 CcaLACs, respectively, suggesting possible post-transcriptional modification via microRNA. Subcellular localization showed CcaLACs in multiple plant cell compartments. Protein structure predictions revealed up to 10 motifs in CcaLACs, with 18 containing transmembrane helices. Overall, CcaLAC28 and CcaLAC32 are likely involved in the lignification process of phloem (bast) in white jute. Modifying these genes could enhance our understanding of lignification and potentially lead to the development of low-lignin jute fibres, meeting high industrial demands globally.