Larch ( Larix spp.) is a key coniferous timber species and an important model for studying wood formation, a process that depends on the activity of the vascular cambium. However, the regulatory mechanisms underlying age-related changes in cambial activity remain poorly understood. In this study, integrated morphological and transcriptomic analyses were conducted on Larix principis-rupprechtii across stand ages. Morphological examination revealed a significant decline in both cambial cell layer number and density with increasing age. Transcriptomic sequencing identified 1799 differentially expressed genes (DEGs). Fuzzy clustering (Mfuzz) and time-ordered gene coexpression network (TO-GCN) analyses delineated distinct expression patterns and hierarchical regulatory tiers across development. In young forests, MYB transcription factors (TFs) directly regulated hemicellulose hydrolysis and remodeling, with the MYB36-XTH9 module playing a central role. During middle-aged to near-mature stages, RAV TFs orchestrated lignin biosynthesis by modulating five laccase ( LAC ) genes. In mature forests, cell expansion-related genes, regulated by ERFs, NACs, and bHLHs, were upregulated. Concurrently, genes associated with the auxin, jasmonate, abscisic acid, and ethylene signaling pathways showed increased expression. By identifying key genes and pathways, this study elucidates the molecular mechanisms underlying age-dependent vascular cambium activity in L. principis-rupprechtii . The results provide genetic resources and a theoretical framework for improving wood quality through targeted manipulation of cambial activity. Furthermore, this work offers novel insights into the evolutionary dynamics and biotechnological applications of age-related cambium regulation in larch species.
Zhou et al. (Sun,) studied this question.