Plastid 2-oxoglutarate-dependent dioxygenases mediate stereoselective C14β-hydroxylation in cardenolide biosynthesis
Abstract
Cardenolides, widely distributed across multiple plant families, have long been utilized in traditional and modern medicine for treating heart failure and various cancers. Despite progress in understanding the initial steps of cardenolide biosynthesis, the evolutionary mechanisms behind the production of structurally diverse cardenolides across plant families remain poorly understood. Here, we report the genome sequence of Periploca sepium Bunge, a member of the Apocynaceae family, and identify two closely linked genes— PsCYP87 and Ps14βPH —governing sterol side-chain cleavage and C14β-hydroxylation, respectively. Although CYP87A enzymes are known to initiate cardenolide biosynthesis in other species, PsCYP87, now classified in the CYP87N subfamily, appears to have evolved independently within the Apocynaceae. Moreover, Ps14βPH contains an unusual plastid-targeting transit peptide and is specific to the family. Notably, 14β-hydroxy pregnenolone, the product of Ps14βPH, was not previously considered as a biosynthetic precursor for cardenolides. However, through gene silencing and isotope labeling experiments, we show that it functions as a precursor in P. sepium . Our findings uncover diverse evolutionary mechanisms—such as the co-opted enzyme pair, atypical subcellular localization, and enzyme convergence at the subfamily level—that underscore the remarkable ability of plants to independently evolve complex metabolic pathways for specialized metabolism. These findings also identify enzyme classes that catalyze a rare stereo-inverted hydroxylation reaction unique to cardenolide biosynthesis.
Article Details
Journal Info
Proceedings of the National Academy of Sciences
National Academy of Sciences
Authors (12)
Jianhua Wang
Xuan Zhou
State Key Laboratory of Agricultural and Forestry Biosecurity, Key Laboratory of Ministry of Education for Genetics, Breeding and Multiple Utilization of Crops, Plant Immunity Center, Fujian Agriculture and Forestry University
Wenjuan Ji
Shanghai Collaborative Innovation Center of Agri-Seeds, School of Agriculture and Biology, Shanghai Jiao Tong University
Jianghu Bian
Shanghai Collaborative Innovation Center of Agri-Seeds, School of Agriculture and Biology, Shanghai Jiao Tong University
Changjian Zhang
Shanghai Collaborative Innovation Center of Agri-Seeds, School of Agriculture and Biology, Shanghai Jiao Tong University
Hong Zhou
Shanghai Collaborative Innovation Center of Agri-Seeds, School of Agriculture and Biology, Shanghai Jiao Tong University
Changheng Shan
Shanghai Collaborative Innovation Center of Agri-Seeds, School of Agriculture and Biology, Shanghai Jiao Tong University
Ning An
Rongchi Li
Shanghai Collaborative Innovation Center of Agri-Seeds, School of Agriculture and Biology, Shanghai Jiao Tong University
Quanzhe Li
CCNU-uOttawa Joint Research Centre, State Key Laboratory of Green Pesticide, Engineering Research Center of Photoenergy Utilization for Pollution Control and Carbon Reduction, Ministry of Education, International Joint Research Center for Intelligent Biosensing Technology and Health, College of Chemistry, Central China Normal University (CCNU), 152 Luoyu Road, Wuhan, Hubei 430079, P. R. China
Si-Hua Hou
School of Pharmaceutical Sciences, Shanghai Key Laboratory of Chiral Drugs and Engineering, Shanghai Frontiers Science Center of Drug Target Identification and Delivery, National Key Laboratory of Innovative Immunotherapy
Zhenhua Liu
Shanghai Collaborative Innovation Center of Agri-Seeds, School of Agriculture and Biology, Shanghai Jiao Tong University