Computational identification and antifungal bioassay reveals phytosterols as potential inhibitor of Alternaria arborescens

Abstract

Alternaria arborescens is a major pathogen for crops like tomato, tangerine and so on and its control is mostly dependent on the application of chemical agents. Plants as the sources of natural products are very attractive option for developing eco-friendly and natural antifungal agents. In this study, we modeled three-dimensional structure of chorismate synthase (CS) enzyme from A. arborescens. Docking studies of phytosterols, namely, γ-sitosterol and β-sitosterol, with CS showed them to be potential inhibitor of CS. To explore the stability and conformational flexibility of all the AaCS complex systems, molecular dynamics simulations were performed. None of the putative inhibitors as well as β- and γ-sitosterol showed interaction with the FMNH₂ binding pocket of the tomato CS (major host of A. arborescens) indicating their suitability as antifungal compounds inhibiting the shikimate pathway without causing any harm to the host. An in vivo antifungal bioassay showed a significant reduction in fungal growth in the presence of β-sitosterol (500 ppm) which resulted in ∼23% and ∼17% reduction in fungal fresh and dry weight, respectively, at 8 days after inoculation. This study provides experimental evidence establishing natural sterols like β-sitosterol can be useful in curbing A. arborescens damage in an eco-friendly manner.

Communicated by Ramaswamy H. Sarma

Keywords:

• Alternaria arborescens
• chorismate synthase
• natural products
• phytosterols
• 3D modeling
• molecular dynamics

Acknowledgments

The study is a part of the project entitled “Development of gene-chip for detection of major fungal plant pathogens” under ICAR funded Network Project on Application of Microorganisms in Agriculture and Allied Sector. SKS and AM acknowledges the RUSA 2.0 sanctioned vide letter no F.24-51/2014-U, Policy (TN Multi-Gen), Dept of Education, GOvt. of INdia Dated 09.10.2018.

Disclosure statement

No potential conflict of interest was reported by the authors.