Analysis of \u03b2-tubulin-carbendazim interaction reveals that binding site for MBC fungicides does not include residues involved in fungicide resistance

David Vela-Corcía,Alejandro Pérez-García,Diego Romero,Antonio De Vicente

doi:10.1038/s41598-018-25336-5

Abstract

Methyl benzimidazole carbamate (MBC) fungicides are fungicidal compounds that exert their biological activities by preventing cell division through the inhibition of tubulin polymerization, which is the major component of microtubules. Several mutations in the β-tubulin gene contribute to MBC resistance, the most common and significant of which occur at residues 198 and 200. Despite nearly 50 years of agricultural use, the binding site of MBCs and the precise mechanism by which those mutations affect fungicide efficacy have not been determined. The aim of this work was to clarify the mode of action and the mechanism of resistance to MBC fungicides in Podosphaera xanthii, the primary causal agent of cucurbit powdery mildew, using a combination of biochemical, biophysical and computational approaches. The results allow us to propose an MBC binding site in β-tubulin that lies close to the GTP binding site and does not include residue 198 involved in MBC resistance.

Highlights

Methyl benzimidazole carbamate (MBC) fungicides were introduced in the market in the early 1970s and became widely used in agriculture
We aimed to investigate the mode of action and the mechanism of resistance to MBC fungicides using P. xanthii tubulins as a model system to analyze fungicide-protein interactions
We confirmed that the E198A mutation found in the β-tubulin gene was responsible for the resistance to MBC fungicides observed in P. xanthii

Summary

Introduction

Methyl benzimidazole carbamate (MBC) fungicides were introduced in the market in the early 1970s and became widely used in agriculture. A few years following their introduction into the market, loss of disease control with MBC fungicides was reported for several crops, with pathogens that have numerous cycles per year, such as grey mould. At least 100 species of plant pathogenic fungi have developed a certain degree of resistance to MBCs (www.frac.info). Several mutations in the β- tubulin gene have been associated with resistance to MBC fungicides in phytopathogenic fungi[5]. Powdery mildew fungi (Erysiphales) are a particular group of plant pathogens that annually threaten a variety of crops worldwide, causing economically important losses. We aimed to investigate the mode of action and the mechanism of resistance to MBC fungicides using P. xanthii tubulins as a model system to analyze fungicide-protein interactions. We demonstrate that the E198A mutation slightly alters the structure of the β-tubulin, which enables resistance to the fungicide

Objectives

Methods

Results

Conclusion