1-Deoxy-D-Xylulose-5-Phosphate Synthase 1 as a Crucial Regulatory Enzyme for Terpenoid Biosynthesis in the Leaves of Cinnamomum burmannii

Cinnamomum burmannii, renowned for its high essential oil content in leaves, is a pivotal species utilized for aromatic medicinal and industrial materials. This study focused on the functional identification of key regulatory enzyme 1-deoxy-D-xylulose-5-phosphate synthase (DXS) for terpenoid biosynthesis in the leaves of C. burmannii. A comprehensive approach, integrating terpenoid profiling assay and synthesis pathway construction, correlation analysis of terpenoid content and gene expression, and genome-wide analysis of DXS family across four developmental stages of leaves in three accessions of C. burmannii, led to the identification of CbDXS1 as a candidate regulatory gene for terpenoid biosynthesis. Overexpressing CbDXS1 in Arabidopsis enhanced plant growth, DXS enzyme activity, and chlorophyll content, and elevated transcriptional levels of terpenoid biosynthesis-related genes, leading to significant increases in terpenoid metabolites in transgenic leaves. Additionally, alterations in metabolite contents in the pathways of glycolysis, the tricarboxylic acid cycle, oxidative pentose phosphate, the Calvin cycle, oxidative phosphorylation, amino acid metabolism, and phytohormone biosynthesis suggested a potential redirection of carbon flux from primary metabolism to terpenoid biosynthesis and changes in endogenous phytohormone contents, the diterpene biosynthesis pathway, and amino acid metabolism, which may collectively contribute to terpenoid accumulation and phenotypic improvement in transgenic Arabidopsis. Our findings elucidated the multifaceted roles of CbDXS1 in modulating carbon flux and phytohormone biosynthesis for terpenoid production and plant development, offering potential strategies for engineering essential oil accumulation in the leaves of C. burmannii.