## 1 Introduction  
Secondary metabolites are essential organic matter during plant growth and development [1]. The secondary metabolic pathways of plants have self-protection mechanisms against various environmental threats such as environmental changes and biotic stress [2]. In particular, volatile organic compounds (VOCs) are one of the most widely studied substances, giving plants a variety of odors that play an essential role in plant growth and development [3]. VOCs are usually divided into terpen, benzenoid aromatics, and fatty acids [4]. Terpenes account for the largest proportion of VOCs and are the most widely studied substances [5]. Terpenes are widely distributed in the plant field and are synthesized from isoprene (C\({}_{5}\)). According to the number of carbon atoms, they can be divided into monoterpenes (C\({}_{10}\)), sesquiterpenes (C\({}_{15}\)), and diterpenes (C\({}_{20}\)), triterpenes (C\({}_{30}\)), and polyterpenes. At present, the metabolic pathways of terpenes have been well interpreted. There are two metabolic pathways: the methylerythnitol phosphate (MEP) pathway, which occurs in the plastid, and the mevalonate (MVA) pathway, which occurs in the cytosol [6]. The MEP pathway uses glyceraldehyde-3-phosphate and pyruvate as precursors to synthesize monoterpenes and diterpenoids by modifying various enzymes in the downstream pathway [7]. The MVA pathway uses acetyl-CoA as a precursor to synthesize sesquiterpenes [8]. The synthesis and accumulation of different types of terpene depend on the action of critical enzymes in the metabolic pathway. These enzymes are generally at the branching points of the synthetic pathway, catalyzing the formation of various precursors and intermediates. Therefore, the synthesis of aroma can be studied by cloning analysis and expression regulation of crucial enzyme genes [9]. Among them, 1-deoxy-D-xylulose-5-phosphate synthase (_DXS_) and farnesyl pyrophosphate synthase (_FPS_) are crucial enzymes in the upstream and downstream pathways of the pathway and play an essential role in terpene synthesis. _DXS_ is the first crucial rate-limiting enzyme in the MEP pathway; It catalyzes pyruvate and glyceraldehyde 3-phosphate to 1-deoxyxylulose-5-phosphate [10]. The _DXS_ family is a very tiny family currently known to have three subfamilies [11]. The _DXS_ family is mainly involved in the synthesis of isoprenoids required for primary metabolites, the _DXS_2 family is thought to be involved in plant-specific isoprenoid synthesis, and the _DXS3_ family is involved in hormone synthesis [12; 13]. Related studies show that overexpression of _DXS_ can affect plants. For instance, in the study of overexpression of the _DXS_ gene in _Populus trichocarpa_, it was found that the _DXS_ gene improves the tolerance of _Populus trichocarpa_ to abiotic, biotic stress and is widely involved in plant growth and development, and physiological processes of stress [14]. In _genanium_, isolation and functional verification of its _DXS_ gene (_GrDXS_), and overexpression of _GrDXS_ in _genanium_ and _Withania somifera_ by genetic transformation, showed that _GrDXS_ overexpression results in increasing essential oils in _genanium_ and withanolides in _W. somifera_[15]. _FPS_ is mainly based on GPP and IPP for catalytic synthesis of FPP, which is an essential rate-limiting step in terpene metabolism related to downstream terpenoid modification and plant stress resistance [16]. Silencing the FPS gene of Arabidopsis thaliana produces a greening phenotype associated with changes in chloroplast morphology and structure, and results in significant changes in cytoplasmic and cytoplasmic isoprene types. [17]. _DXS_ and _FPS_ are more widely studied in flowers and some model plants. However, Rutaceae plants with well-developed oil glands and unique fragrances have often been ignored, except for _Citrus_[18].