###### Abstract
reinhardtii_ is a single-celled eukaryotic green alga, known as \"photosynthetic yeast\" due to its simple cultivation conditions, short growth cycle, rapid growth, and high photosynthetic efficiency. It has a complex post-translational modification system that can accurately process and modify eukaryotic proteins to ensure that recombinant proteins have the same activity as natural proteins [10]. The growth and metabolism of Chlamydomonas reinhardtii do not produce toxic waste, and the extraction and purification process of the product is relatively simple. There is no risk of environmental pollution from by-products. These advantages indicate that it is a promising terpenoid production system [7]. Squalene is a critical intermediate in the biosynthesis of sterol in a range of organisms from bacteria to humans [11]. Squalene C30 has been considered for various biological functions, such as a natural antioxidant, anticancer, dietary complement, auxiliary for vaccines, and skin moisturizer for therapeutic, cosmetic, and pharmacological uses as well as a protective response to cardiovascular diseases [12; 13]. Shark liver oil is the main source of squalene, with a content of up to 80% [14]. Among vegetable sources of squalene, extra virgin olive oil (EVOO) is one of the richest ones, containing squalene in 0.1-1.2%, along with amaranth oil that contains a higher amount (7-8%) but is produced with lower yields compared to olive oil [14; 15]. The determination of squalene content in olive oil by transmethylation and GC analysis is 2.88 \(\pm\) 0.08 (mg g\({}^{-1}\)) [16]. Eating olive oil is beneficial to prevent colon cancer and breast cancer, and also has the ability to reduce blood pressure [17]. Microorganisms, including microalgae, have also been investigated for the biosynthesis of squalene at a commercial level [18]. Compared with extracting squalene from vegetable oil, the production cycle of squalene using microorganisms is shorter, the cost is lower, it is economical, environmentally friendly, and easier to regulate [19]. To assure a sustainable supply of squalene and fulfill its industrial demand, substitute sources are required, such as marine organisms. The amount of squalene in microorganisms varies greatly depending on the species. The contents of squalene obtained from _Torulaspora delbrueckii_ and _S. cerevisiae_ were 0.24 and 0.04 ug/mg, respectively [20]. A higher amount of squalene (171 ug mg\({}^{-1}\) dry weight) in the cells of _Aurantiolchytrium_ sp. strain 18W-13a was accumulated [21]. Previous studies reported that _Euglena_ and _Botryococcus braunii_ were able to accumulate squalene in their cells [11]. Functionally, the characterization of a few genes, which are considered for the metabolism of squalene, has been documented in microalgae [22]. The two general biosynthetic pathways, including the mevalonate (MVA) pathway and the methylerythitol phosphate (MEP) pathway, are involved in the production of squalene in plants, while green algae entertain the MEP biosynthetic pathway only [23]. IPP and DMAPP are the universal precursors of terpenoids, which are regulated by the MEP/MVA biosynthetic pathway. The building blocks of particular terpenoids are the GPP, FPP, and GGPP, which are formed by the condensation of IPP and DMAPP. The heterologous terpenoid synthesis usually involves the whole biosynthetic pathways or specific enzyme expressions, which link to endogenous terpenoid metabolism and change the substrate of prenyl phosphate into the required product [24]. In order to obtain higher yields of the desirable product, it is essential to modify the upstream terpenoid biosynthetic pathways (MEP) through genetic and metabolic engineering [6]. In microalgae, to increase sustainable terpenoid production, metabolic engineering is required in the MEP pathway in order to improve the carbon flow toward the synthesis of terpenoids [25]. In the current study, we have investigated MYB transcriptional factors as a prospective elicitor of the MEP/MVA biosynthetic pathway in the plants.