Identification of key genes controlling monoterpene biosynthesis of Citral-type Cinnamomum bodinieri Levl. Based on transcriptome and metabolite profiling

Abstract The citral-type is the most common chemotype in Cinnamomum bodinieri Levl (C. bodinieri), which has been widely used in the daily necessities, cosmetics, biomedicine, and aromatic areas due to their high citral content. Despite of this economic prospect, the possible gene-regulatory roles of citral biosynthesis in the same geographic environment remains unknown. In this study, the essential oils (EOs) of three citral type (B1, B2, B3) and one non-citral type (B0) varieties of C. bodinieri were identified by GC-MS after hydrodistillation extraction in July. 43 components more than 0.10% were identified in the EOs, mainly composed of monoterpenes (75.8–91.84%), and high content citral (80.63–86.33%) were identified in citral-type. Combined transcriptome and metabolite profiling analysis, plant-pathogen interaction(ko04626), MAPK signaling pathway-plant(ko04016), starch and sucrose metabolism(ko00500), plant hormone signal transduction(ko04075), terpenoid backbone biosynthesis (ko00900) and monoterpenoid biosynthesis (ko00902) pathways were enriched significantly. The gene expression of differential genes were linked to the monoterpene content, and the geraniol synthase (CbGES), alcohol dehydrogenase (CbADH), geraniol 8-hydroxylase-like (CbCYP76B6-like) and 8-hydroxygeraniol dehydrogenase (Cb10HGO) were upregulated in the citral-type, indicating that they were associated with high content of geraniol and citral. The activities of CbGES and CbADH in citral type were higher than in non-citral type, which was corroborated by enzyme-linked immunosorbent assay (ELISA). This study on the accumulation mechanism of citral provides a theoretical basis for the development of essential oil of C. bodinieri.