Synthetic biology and metabolic engineering strategies in identifying and producing plant natural products; with emphasis on the CRISPR/Cas systems

Plant natural products (PNPs) are one of the primary sources of cosmetics, food additives, and pharmaceuticals, thus they have received much attention in synthetic biology in recent years. Various plant in vitro cultures, elicitation strategies, and genetic engineering are considered suitable methods for increased production of valuable PNPs. Traditional methods have been successfully developed to enhance the amount of PNPs for many years, however, researchers are replacing them with more cost-effective and efficient techniques. Here, we attempted to discuss the approaches applied to manipulate PNPs production, with an emphasis on genome engineering using sequence-specific nucleases, particularly CRISPR/Cas system. As powerful gene editing tools, TALEN, meganucleases, ZFNs, and CRISPR nucleases have been developed for targeted modifications of DNA sequence in plant cells. Among them, the CRISPR/Cas9 system has been engaged in a wide variety of research to elucidate and modify the biosynthetic routes of PNPs in medicinal plants. This technology has opened up significant prospects for promoting the yield and quality of PNPs in different plant species. Through precise genetic modifications to critical enzymes and transcription factors, CRISPR technology is increasing our understanding of PNPs biosynthesis pathways in plants, preparing the practical way for developing new drugs and reconstruction of traditional medicine. In the meantime, this review could provide new insights into future applications of CRISPR in plants. In conclusion, CRISPR technology has abundant potential for application in metabolic engineering as well as PNP investigation, leading to further advances in biomedicine science. As technological progress proceeds and challenges are overcome, CRISPR technology could become increasingly important in medicinal plant research. • The use of plant natural products faces challenges like low yields, resource-intensive extraction, and plant overharvesting. • Synthetic biology and genome engineering with sequence-specific nucleases are new tools to produce plant metabolites in large scale. • CRISPR/Cas9 nucleases could help to find an efficient way to produce bioactive agents in plants.