## 2 Botanical Biopesticides
### Botanical Biopsticides and Synthetic Biology
Their products are mainly plant extracts, such as _resorcin_, _reynoutriajaponicHoutt_, _organism vulgar_, etc. Currently, direct extraction from target plants or chemical synthesis is the main source of botanical biopesticides. In terms of direct extraction, some compounds are only present in certain parts of the target plants, such as _glycyrrheticic acid_ (only in the roots of _licorice_), _paclitaxel_ (only produced in the bark of _haulhina blakeana [PERSON]_) [49], _saponin_ (extracted from the seeds of _Camelia sinensis_) [38], _isobavachalcone_ (extracted from the source of the _posalea corylifolia L._ seeds) [50; 51], and _curcumol_ (produced only in _Curcuma longa_) [52]. Therefore, direct extraction would be not only be wasteful to plant resources but also place great pressure on the environment due to a large number of organic reagents. In addition, natural products accumulate slowly and at low levels in the plant, and the use of artificial cultivation introduces problems such as long culture cycles, wasted land resources, and vulnerability to weather factors. Additionally, the fact that plants contain many structurally similar compounds creates great difficulties in isolation and increases costs [51]. These factors have led to difficulties in meeting research and market demands using traditional botanical production methods and an urgent need for an efficient and green sustainable method to natural plant natural products [53]. In terms of chemical synthesis, most natural products are characterized by complex structures and many chiral centers, which can lead to deactivated, difficult-to-separate, or even toxic spin isomers during the process of synthesis. At the same time, natural products require complex synthetic steps, low conversion rates, and high energy consumption. Additionally, the organic reagents used in synthetic processes also can put great pressure on the environment, making it difficult to meet the needs of industrialization [54]. The development of synthetic biology has prompted new ideas to solve the aforementioned problems. Synthetic biology is a discipline that genetically designs and modifies cells or living organisms by synthesizing biological functional components, devices, and systems to give them biological functions that meet human needs or even create new biological systems [55]. This discipline constructs cell factories or in vitro synthetic systems by systematically designing metabolic pathways and synthetic assemblies from a large number of genes, which can theoretically synthesize arbitrary compounds and will revolutionize the fields of drug manufacturing, industrial chemistry, and materials science. Biological systems are complex and unpredictable wholes. The continuous re-optimization of core molecular components through synthetic biotechniques and strategies can enhance the biological functions of existing systems, simulate and construct biological components that do not exist in nature, and create new biological functions and systems [56]. Plant natural products have long been a challenging and important area of study in synthetic biology research. Using microorganisms to synthesize structurally complex plant natural products can not only achieve continuous large-scale production but also obtain high purity and yield. At the same time, this process can obtain some structural analogues that are difficult to find in nature. Progress has been made in the heterologous synthesis of plant natural products in microbial cells using synthetic biology methods, especially in botanical pesticides. For example, the botanical biopesticide _celangulin_, a class of \(\beta\)-dihydroagaofuran sesquiterpene compounds, has a biosynthetic pathway that follows the common route of sesquiterpene compound synthesis: skeleton synthesis, cyclization, post-modification [57]. Firstly, IPP and DMAPP, the common precursors of all terpen, are synthesized via the MVA pathway in the cytoplasm or MEP pathway in the limb.