Action of the fungal compound citrinin, a bioherbicide candidate, on photosystem II

• Published in: Pest management science 2024-01, Vol.80 (1), p.133-148
• Main Authors: Yang, Qian, Guo, Yanjing, Wang, He, Luo, Zhi, Chen, Ying, Jiang, Mengyun, Lu, Huan, Valverde, Bernal E., Qiang, Sheng, Strasser, Reto Jörg, Chen, Shiguo
• Format: Article
• Language: English
• Subjects: Bioactive compounds; Bioassays; Chlorophyll; chlorophyll a fluorescence; Citrinin; D1 protein; Fungi; Herbicides; Histidine; Hydrogen bonds; Inactivation; Lead compounds; molecular docking; Molecular modelling; natural product; Natural products; Pesticides; Phenolic compounds; Phenols; Photosystem II; Phytotoxicity; Phytotoxins; Plant species; Proteins; Reaction centers; Sustainable agriculture; Weed control
• ISSN: 1526-498X; 1526-4998
• DOI: 10.1002/ps.7513

BACKGROUND Bioherbicides are becoming more attractive as safe weed control tools towards sustainable agriculture. Natural products constitute an important source chemicals and chemical leads for discovery and development of novel pesticide target sites. Citrinin is a bioactive compound produced by fungi of the genera Penicillium and Aspergillus. However, its physiological‐biochemical mechanism as a phytotoxin remains unclear. RESULTS Citrinin causes visible leaf lesions on Ageratina adenophora similar to those produced by the commercial herbicide bromoxynil. Phytotoxicity bioassay tests using 24 plant species confirmed that citrinin has a broad activity spectrum and therefore has potential as a bioherbicide. Based on chlorophyll fluorescence studies, citrinin mainly blocks PSII electron flow beyond plastoquinone QA at the acceptor side, resulting in the inactivation of PSII reaction centers. Furthermore, molecular modeling of citrinin docking to the A. adenophora D1 protein suggests that it binds to the plastoquinone QB site by a hydrogen bond between the O1 hydroxy oxygen atom of citrinin and the histidine 215 of the D1 protein, the same way as classical phenolic PSII herbicides do. Finally, 32 new citrinin derivatives were designed and sorted according to free energies on the basis of the molecular model of an interaction between the citrinin molecule and the D1 protein. Five of the modeled compounds had much higher ligand binding affinity within the D1 protein compared with lead compound citrinin. CONCLUSION Citrinin is a novel natural PSII inhibitor that has the potential to be developed into a bioherbicide or utilized as a lead compound for discovery of new derivatives with high herbicidal potency. © 2023 Society of Chemical Industry. Citrinin is a novel natural photosynthetic inhibitor because it strongly blocks photosystem II electron transport beyond QA by binding to the QB site of the D1 protein.