Transcriptome analysis of pericarps containing essential oils with high/low citral proportions in wild Litsea cubeba

Litsea cubeba (Lour.) Pers. is one of the main citral type essential oil trees in the Lauraceae family. Citral is the dominant component of L. cubeba essential oil (LcEO), which is mainly extracted from the fruit pericarp (mesocarp and exocarp). Notably, LcEO is widely used in medical products, food preservatives, feed additives, and other industrial compounds. However, substantial differences in the citral proportion (CitralP) among L. cubeba-growing regions have limited the improvement of LcEO quality. 16 trees with significant differences in CitralP were randomly selected for a transcriptome analysis among 141 wild L. cubeba trees. Differential gene expression, functional enrichment, dynamic trends, and gene expression (qRT-PCR) were analyzed. The transcriptome data were clustered on the basis of the longitude, latitude, and elevation of the regions in which L. cubeba trees were sampled, rather than according to CitralP. Seven candidate differentially expressed genes (DEGs) were selected, including genes encoding ankyrin repeat-containing protein INT 1-like (ANK1), S-scoulerine 9-O-methyltransferase-like protein (SMT), auxin-responsive protein IAA20, pantothenic kinase 2 (PANK2), probable 1-deoxy-D-xylulose-5-phosphate synthase 2 (DXS2), and two β-cubebene synthases. Of these DEGs, ANK1, SMT, and IAA20 may be critical genes. Specifically, IAA20 may directly affect citral biosynthesis or, similar to ANK1, it may control citral production via auxin signaling. The positive regulatory effect of ANK1 on CitralP may be associated with the regulation of acetyl CoA or environmental stress responses. SMT influences alkaloid biosynthesis, but its potential role in the positive regulation of citral biosynthesis is unclear. Our study generated transcriptome profiles of L. cubeba trees that differed in terms of CitralP between difference growing region. [Display omitted] •ANK1, SMT, and IAA20 may be key regulators of citral biosynthesis and accumulation in L. cubeba fruit pericarp.•Regulatory effects of ANK1 on CitralP may involve acetyl CoA regulation or environmental stress responses.•IAA20 may directly affect citral biosynthesis.•SMT may positively regulate CitralP, but its potential role is unclear.