Genome-Wide Identification, Expression Profiling, and microRNA397-Mediated Regulation of Laccase Genes in Pinus massoniana

Laccases (EC 1.10.3.2, LAC) are copper-containing glycoproteins involved in lignin biosynthesis, and as such, they play important roles in plant development and stress responses. In this study, a genome-wide analysis of the LAC gene family was performed in Pinus massoniana (Chinese red pine), identifying 78 PmaLAC genes, all predicted to encode cell membrane-localized proteins. These genes were unevenly distributed across eight chromosomes, with notable clusters on chromosomes 7 and 8, indicating gene duplication-driven expansion in P. massoniana. Phylogenetic analysis revealed that PmaLAC genes are classified into five subfamilies, reflecting the lineage-specific expansion and evolutionary divergence of gymnosperm LAC genes. Conserved motif and gene structure analyses showed high conservation among PmaLAC proteins. Promoter analysis identified numerous cis-acting elements related to hormone signaling, stress, and light responses. RNA-seq analysis revealed distinct tissue-specific expression patterns for PmaLAC gene family members. Moreover, degradome analysis combined with dual-luciferase assays supported the interaction between miR397c-9 and PmaLAC31, suggesting that miR397c-9 negatively regulates PmaLAC31 and indicating a potentially conserved miRNA-mediated regulatory mechanism. Overall, this study provides a systematic overview of the composition, evolution, and potential regulation mechanisms of the PmaLAC gene family in P. massoniana, providing a useful resource for future functional characterization of PmaLAC genes.