Identification and Analysis of the Terpene Synthases (TPS) Gene Family in Camellia Based on Pan-Genome

TL;DR

This study identifies and analyzes terpene synthase genes in Camellia species, revealing differences between wild and cultivated tea plants and how these genes contribute to aroma-related genetic diversity.

Contribution

The study provides a pan-genome resource for Camellia TPS genes and highlights domestication-driven genetic changes.

Findings

Wild Camellia species have more TPS genes than cultivated ones, suggesting a contraction in cultivated accessions.

TPS-b and TPS-a subfamilies dominate, while TPS-c is rare and highly conserved.

TPS expression is higher in cultivated tea, especially in mature leaves and stems.

Abstract

Terpenes are major determinants of tea aroma, and terpene synthases (TPSs) catalyze key steps in terpenoid biosynthesis. To capture gene-family variation beyond a single reference, we performed a pan-genome–based analysis of TPS genes across nine Camellia genomes (three wild tea relatives and six cultivated Camellia sinensis accessions) and integrated pan-transcriptome profiling across eight tissues. We identified 381 TPS genes; wild species contained more TPSs than cultivated accessions (mean 58.3 vs. 34.3), suggesting a putative contraction. Phylogenetic analysis with Arabidopsis TPSs classified Camellia TPSs into five subfamilies, dominated by TPS-b (149) and TPS-a (140), whereas TPS-c was rare (8). Gene-structure and physicochemical analyses revealed marked subfamily divergence, with TPS-c showing highly conserved coding-region length. Orthology clustering assigned 355 TPSs to 19 orthogroups, including five core groups (190 genes, 53.5%) and 14 dispensable groups (165 genes, 46.5%); core/non-core status was significantly associated with subfamily composition. Tandem and proximal duplication contributed most to TPS expansion (29.4% and 29.1%), and all orthogroups exhibited copy-number variation, with pronounced lineage-specific expansions. Ka/Ks analyses indicated pervasive purifying selection (median 0.516) but heterogeneous constraints among subfamilies. Finally, cultivated tea showed higher TPS expression in most tissues, especially mature leaf and stem, and TPS-g displayed the broadest and strongest expression. Together, these results provide a pan-genome resource for Camellia TPSs and highlight how domestication, duplication, and CNV shape terpene-related genetic diversity.

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