MYB Transcriptional Factors Affects Upstream and Downstream MEP Pathway and Triterpenoid Biosynthesis in Chlamydomonas reinhardtii

Abstract

Terpenoids are enormous and different types of naturally occurring metabolites playing an important role in industrial applications. Cost-effective and sustainable production of terpenoids at commercial scale is the big challenge because of its low abundance from their natural sources. Metabolic and genetic engineering in microorganisms provide the ideal platform for heterologous overexpression protein systems. The photosynthetic green alga Chlamydomonas reinhardtii is considered as a model host for the production of economic and sustainable terpenoids, but the regulation mechanism of their metabolisms is still unclear. In this study, we have investigated the genetic and metabolic synthetic engineering strategy of MYB transcriptional factors (MYB TFs) in terpenoids’ synthesis from C. reinhardtii for the first time. We heterologous overexpressed MYB TFs, specifically SmMYB36 from Salvia miltiorrhiza in C. reinhardtii. MYB upregulated the key genes involved in the 2-C-methyl-D-erythritol 4-phosphate (MEP) pathway. Expression of the SQS gene, which is involved in the downstream triterpenoid synthesis pathway, highly accumulated in MYB-overexpression lines of C. reinhardtii. The contents of squalene increased about 90.20 μg/g in MYB-overexpressed lines. Our results propose the rerouting of the carbon flux toward the biosynthesis of triterpenoids upon overexpression of MYB TFs in C. reinhardtii. Our study suggests imperative novel understandings into the regulation mechanisms of C. reinhardtii triterpenoid metabolism through MYB TFs in photosynthetic green microalgae C. reinhardtii. The role of MYB TFs is investigated for the first time in C. reinhardtii, and provides a prodigious potential for recognizing important transcriptional regulators of the MEP pathway as goals for prospective metabolic and genetic manipulation investigation for increased production of triterpenoids.