Tissue-specific transcriptomics and evolutionary dynamics of terpene synthase genes in Picea purpurea

This study presents a comprehensive transcriptomic atlas of Picea purpurea, an endemic Qinghai-Tibet Plateau conifer, integrating full-length and short-read transcriptome datasets. We identified 39,156 non-redundant transcripts across four tissues (roots, stems, needles, cones), with 61.52% showing broad expression and 6.15% exhibiting tissue specificity. Tissue-specific transcripts were markedly enriched in secondary metabolism, particularly terpenoid biosynthesis. Phylogenomic analysis of 1642 terpene synthase (TPS) genes from 25 gymnosperms (covering 75% of extant orders) yielded an updated classification of three gymnosperm-specific subfamilies: TPS-d1 (monoterpene synthases), TPS-d2 (sesquiterpene synthases), and TPS-d3 (diterpene synthases). Pan-genome comparisons across six Picea species identified 74 TPS orthogroups, including 6 core conserved families and 38 lineage-specific expansions. These findings elucidate the molecular basis of terpenoid diversification in this ecologically pivotal genus.