Microtubule‐assisted mechanism for toxisome assembly in Fusarium graminearum

Abstract

In Fusarium graminearum, a trichothecene biosynthetic complex known as the toxisome forms ovoid and spherical structures in the remodelled endoplasmic reticulum (ER) under mycotoxin‐inducing conditions. Previous studies also demonstrated that disruption of actin and tubulin results in a significant decrease in deoxynivalenol (DON) biosynthesis in F. graminearum. However, the functional association between the toxisome and microtubule components has not been clearly defined. In this study we tested the hypothesis that the microtubule network provides key support for toxisome assembly and thus facilitates DON biosynthesis. Through fluorescent live cell imaging, knockout mutant generation, and protein–protein interaction assays, we determined that two of the four F. graminearum tubulins, α1 and β2 tubulins, are indispensable for DON production. We also showed that these two tubulins are directly associated. When the α1–β2 tubulin heterodimer is disrupted, the metabolic activity of the toxisome is significantly suppressed, which leads to significant DON biosynthesis impairment. Similar phenotypic outcomes were shown when F. graminearum wild type was treated with carbendazim, a fungicide that binds to microtubules and disrupts spindle formation. Based on our results, we propose a model where α1–β2 tubulin heterodimer serves as the scaffold for functional toxisome assembly in F. graminearum.

Vacuole Proteins with Optimized Microtubule Assembly Is Required for Fum1 Protein Localization and Fumonisin Biosynthesis in Mycotoxigenic Fungus Fusarium verticillioides

“…In HeLa cell, MT is crucial for the spatial distribution and biological functions of purinosomes [ 43 ]. Our recent study demonstrated that MT participated in toxisomes formation and DON biosynthesis in F. graminearum [ 44 ]. In this work, we analyzed the regulatory role of MT network in vacuole morphology via carbendazim treatment.…”

“…We speculated that fragmented vacuoles could facilitate FB 1 biosynthesis, yet there is no close correlation between the expression levels of FvFum1 and vacuole morphology in F. verticillioides . Additionally, in F. graminearum , low concentrations of carbendazim boosted DON production, but high concentrations significantly reduced it [ 44 ]. Our experiments utilized a 1 μg/mL carbendazim concentration, resulting in increased FB1 production.…”

“…Our previous study showed that α1-β2 tubulin heterodimer is critical for toxisome formation and DON biosynthesis in F. graminearum [ 44 ]. However, gene deletion assays in F. verticillioides revealed that three tubulin subunits were involved in FB 1 biosynthesis.…”

Functional Roles of α 1 -, α 2 -, β 1 -, and β 2 -Tubulins in Vegetative Growth, Microtubule Assembly, and Sexual Reproduction of Fusarium graminearum

“…Deletion of β 1 -or β 2 -tubulin (Δβ 1 and Δβ 2 mutants) did not affect microtubule assembly in F. graminearum (33). Moreover, recent studies showed that Δα 1 , Δα 2 , Δβ 1 and Δβ 2 mutants play different roles in toxisome formation of F. graminearum (34). The different phenotypes implied that α 1 -, α 2 -, β 1 -, and β 2 -tubulin may be functionally divergent.…”

Inactivation effects of plasma-activated water on Fusarium graminearum

“…Fusarium graminearum is an ascomycetous fungus that is the major cause of Fusarium head blight (FHB) on wheat and barley, as well as stalk and ear rot disease on maize. This fungus not only causes crop yield and quality losses but also contaminates grain with mycotoxins, rendering them unfit for food or feed (Etzerodt et al, 2016;Kim and Vujanovic, 2016;Masci et al, 2015;Zhou et al, 2021). Benzimidazoles and sterol demethylation inhibitors are widely used for the control of FHB (Blandino et al, 2006;Bian et al, 2021).…”