###### Abstract  
Trepenoids 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 midifornia in C. _reinhardtii_. MYB upregulated the key genes involved in the 2-C-methyl-D-erythroid 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 \(\mu\)g/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. s 2024 12 487. 12.21.100782024 12.21.100782024 12.21.100782024 12.21.100782024 12.21.100782024 12.21.100782024 12.21.10782024 12.21.10782024 12.21.10782024 12.210782024 12.21.10782024 12.210782024 12.210782024 12.21078 of sterols, phenolic compounds, and others [2]. Thus, microalgae could be deliberated to increase CO\({}_{2}\) sequestration, able to recover nutrients from waste and yield valuable compounds [3]. Terpenoids are enormous and a different class of naturally occurring metabolites playing an important function in various industrial applications [4]. Most commercially available terpenoids are obtained from higher plants, but their cost-effective and sustainable production for industrial purposes is still challenging because of their low abundance of production from natural sources, extraction and purification obstacles, and degree of labor intensity [5]. In response to these confronts, bioengineering of microorganisms in controlled bioreactors for terpenoid production has appeared as an ideal solution. Microorganisms including bacteria (_Escherichia coli_) and yeast (_Saccharomyces cerevisiae_) are unable to naturally produce plant metabolites. So these organisms are usually selected as heterologous ideal hosts for the production of terpenoids owing to the advantages of complete information regarding their metabolism and genetic tractability [6]. _E. coli_ and _S. cerevisiae_ need sources of organic compounds for their optimized growth. Therefore, the production of terpenoids from these organisms at a commercial level also presents economic challenges. Currently, genetically modified photosynthetic green microbial hosts have become a carbon-neutral alternative to a generally utilized fermentative system. These carbon-neutral alternatives have the potential to transform CO\({}_{2}\) into highly valuable bioproducts [7]. Previous studies have provided evidence of heterologous terpenoid expression for _Synechocystis_ sp. PCC 6803 and _C. reinhardtii_[8; 9]. _C.