MEP successively produces 4-hydroxy-3-methyl-2-butenyl pyrophosphate (HMBPP) under the catalysis of MEP cytidine transferase (MCT), 4-diphosphocytidyl-2-C-methyl-D-erythriitol kinase (CMK), 2C-methyl-D-erythriodi alcohol 2,4-dichlorophosthe synthase (MDS), and hydroxymethylbutynyl diphosphate synthase (HDS), which further catalyzes the formation of IPP through 4-hydroxy-3-methylbut-2-enyl diphosphate reductase (HDR). IPP and its isomerized product DMAPP further form aromatic monoterpenes, diterpenes, and tetraterpenes under the action of GGPPS, geranyl pyrophosphate synthase (GPPS), and TPS (Figure 1). It is worth noting that the MVA and MEP pathways are connected by IPP, which can move between the cytoplasm and the plastids. Retaining the metabolism of the two IPP/DMAP pathways is believed to better control the compartment-specific isoprene pool, allowing it to transform into MEP-derived monoterpenes and diterpenes, carotenoids, plastids containing quinones, and chlorophyll, as well as MVA-derived sesquiterpenes, sterols, brassinosteroids, and triterpenes [5]. Figure 1: Terpenoid biosynthesis pathway. In recent years, genes encoding enzymes of the MVA and MEP pathways, especially those with important regulatory roles, have been the subject of considerable research. As the first enzyme in the MVA pathway, the overexpression of _GIAACT_ in _ganoderma lucidum_ led to an increase in triterpen content [6], indicating a positive correlation between _GIAACT_ expression and triterpen content. HMGR is an endoplasmic reticulum membrane binding enzyme and is widely recognized as the rate-limiting enzyme of the MVP pathway. HMGR is encoded by a small gene family, and although some isomers engage in the synthesis of isoprenoids, the roles of other isomers are still unclear [7]. MVK is the first ATP-dependent enzyme in the MVP pathway and is one of the rate-limiting enzymes that control the entire metabolic pathway. It is highly expressed in _Arabidopsis_ and promotes a significant increase in the content of intermediate metabolites such as dienes in triterpen synthesis [8]. The _PMK_ gene in the fruit of the silenced _Mangifera_ indica showed meaningful changes in terpene metabolites, with a decrease or disappearance of \(\beta\)-caryophyllene, \(\beta\)-pinene, bisabolene, and \(\beta\)-guaiene. However, \(d\)-limonene was newly observed in the silenced fruit. Due to its role in the formation of sesquiterpenes and triterpenes, research on FPPS has been widely studied. For example, when cotton _AaFPPS_ cDNA was transferred to _Artemisia annua_, it was found that the content of sesquiterpene lactone artemisinin in transgenic plants increased by 2 to 5 times [9; 10]. Related results also appeared in _Rosa rugosa_ overexpressing _RrfPPS_[11]. DXS and DXR are considered important rate-limiting enzymes in the MEP pathway. Transient overexpression of _AcDXS1_ leads to a significant increase in monoterpenes in _Nicotiana tabacum_ leaves [12]. Silencing of tomato _SIDXS_ leads to a decrease in sesquiterpene content, and the overexpression of _DXR_ increases paclitaxel synthesis in _Arabidopsis_, all indicating a positive correlation between DXS and DXR expression levels and terpenes. IDI, GGPPS, and TPS are three enzymes that appear in the cytoplasm and plastids and affect the synthesis of terpenoids. GGPPS can catalyze the formation of GGPP from three molecules of IPP and DMAPP, thereby affecting the content of diterpenes. The decrease in _AIGGPPS11_ expression in _Arabidopsis_ not only leads to pale phenotype and developmental delay but also accompanies a decrease in the content of isoprenoid substances derived from plastid GGPP [13]. Research has found that the expression patterns of two _TPS_ genes in _illium brownie var.