Convergent evolution of stereodivergent p-menthane gene clusters in Lamiaceae Samuel Smit 1 , Chanchan Liu 2,3 , Qinan Wu 2,3 , Benjamin R. Lichman 1 1 University of York, United Kingdom, 2 Nanjing University of Chinese Medicine, China, 3 Jiangsu Collaborative Innovation Center of Chinese Medicinal Resources Industrialization, China The medicinal plant Japanese catnip ( Schizonepeta tenuifolia ) produces monoterpenoid p-menthane compounds such as limonene, pulegone and menthone 1 . These have been found to have the opposite stereochemistry to those observed in the closely related Mentha genus 2,3 . The genetic basis for the evolutionary switch that results in the stereochemical differences were investigated by assembling a chromosome level genome for S. tenuifolia . We identified a bipartite biosynthetic gene cluster (BGC) and gene arrays containing homologs of previously identified pathway genes. In vitro assays and virus induced gene silencing (VIGS) of S. tenuifolia validated the function of pathway homologs. Furthermore, we discovered three identical genes within the BGC that can reduce isopiperitenone to isopulegone. These genes have evolved convergently to the enzyme catalysing the equivalent reaction in Mentha . Phylogenetic comparisons to related species and pathway homologs, as well as synteny analyses were carried out. These analyses allowed us to model the evolutionary mechanisms that likely resulted in the S. tenuifolia BGC involved in the stereodivergent biosynthesis of p-menthane. This work sheds light on convergent evolution and BGC formation in plant terpene biosynthesis. References 1. C. Liu, N. Srividya, A. N. Parrish, W. Yue, M. Shan, Q. Wu and B. M. Lange, Phytochemistry, 2018, 150, 23–30. 2. C. Liu, Q. Gao, Z. Shang, J. Liu, S. Zhou, J. Dang, L. Liu, I. Lange, N. Srividya, B. M. Lange, Q. Wu and W. Lin, Frontiers in Plant Science, 2021, 12, 2807. 3. N. Srividya, E. M. Davis, R. B. Croteau and B. M. Lange, Proc Natl Acad Sci USA, 2015, 112, 3332–7.
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