Unveiling the evolution of iridoid biosynthesis in the genus Nepeta: a mini review

Abstract

The genus Nepeta, belonging to the Lamiaceae family, encompasses a diverse group of plants with significant biological activities attributed mainly to their iridoid compounds. This review provides a comprehensive analysis of recent research on iridoid biosynthesis, regulation, and evolutionary aspects within the Nepeta genus. The biological activities of Nepeta species, including repellent, phytotoxic, antimicrobial, and cytotoxic effects, have been extensively investigated, highlighting the potential applications of iridoids. Over the past decade, significant progress has been made in elucidating the molecular basis of iridoid biosynthesis and regulation, thanks to advancements in transcriptomics, genomics, and metabolomics. The presence of distinct chemotype groups within Nepeta has been revealed, characterized by their ability to produce both iridoid aglycones (nepetalactones) and glycosylated iridoids (IAs and IGs), exclusively produce IGs, or lack iridoids. The identification of key enzymes involved in iridoid biosynthesis, such as geraniol synthase (GES) and iridoid synthase (ISY), has played a crucial role in understanding the pathway. Furthermore, the evolutionary aspects of the iridoid biosynthesis loss in some of the Nepeta taxa, and the association of iridoid presence and content with the expression levels of specific genes, have been investigated. However, several areas remain to be explored, including the final steps of iridoid aglycones biosynthetic branch, the production of iridoid glucosides, the role of transcription factors in fine-tuning of iridoid biosynthesis, and the intricate interplay between biosynthetic enzymes. Continued research in these areas will deepen our understanding of iridoid metabolism in Nepeta and unlock their full potential in various fields, including pharmaceuticals, agriculture, and natural product-based industries.