FgPex3, a Peroxisome Biogenesis Factor, Is Involved in Regulating Vegetative Growth, Conidiation, Sexual Development, and Virulence in Fusarium graminearum.

Xiangjiu Kong,Jin Xu,Balazs Brankovics,Wanquan Chen,Anne Van Diepeningen,Jie Feng,Hao Zhang,Theo Van Der Lee,Cees Waalwijk,Xiaoliang Wang,Jingsheng Xu

doi:10.3389/fmicb.2019.02088

Abstract

Peroxisomes are involved in a wide range of important cellular functions. Here, the role of the peroxisomal membrane protein PEX3 in the plant-pathogen and mycotoxin producer Fusarium graminearum was studied using knock-out and complemented strains. To fluorescently label peroxisomes’ punctate structures, GFP and RFP fusions with the PTS1 and PTS2 localization signal were transformed into the wild type PH-1 and ΔFgPex3 knock-out strains. The GFP and RFP transformants in the ΔFgPex3 background showed a diffuse fluorescence pattern across the cytoplasm suggesting the absence of mature peroxisomes. The ΔFgPex3 strain showed a minor, non-significant reduction in growth on various sugar carbon sources. In contrast, deletion of FgPex3 affected fatty acid β-oxidation in F. graminearum and significantly reduced the utilization of fatty acids. Furthermore, the ΔFgPex3 mutant was sensitive to osmotic stressors as well as to cell wall-damaging agents. Reactive oxygen species (ROS) levels in the mutant had increased significantly, which may be linked to the reduced longevity of cultured strains. The mutant also showed reduced production of conidiospores, while sexual reproduction was completely impaired. The pathogenicity of ΔFgPex3, especially during the process of systemic infection, was strongly reduced on both tomato and on wheat, while to production of deoxynivalenol (DON), an important factor for virulence, appeared to be unaffected.

Highlights

Peroxisomes are a class of dynamic single-membrane-bound organelles, found in almost all eukaryotic cells
We investigated the function of PEX3 in F. graminearum, as there are no reports on the role of PEX3 on the peroxisome assembly in F. graminearum or any other filamentous fungi
The PEX3 amino acid sequences from several pathogenic fungi (Magnaporthe oryzae, Neurospora crassa, Aspergillus flavus, A. nidulans and Fusarium oxysporum) were downloaded from the NCBI database, and the phylogenetic tree based on the amino acid sequences revealed that FgPex3 is most closely related to FoPex3 and MoPex3 (Figure 1)

Summary

Introduction

Peroxisomes are a class of dynamic single-membrane-bound organelles, found in almost all eukaryotic cells. Functional Research of FgPex in F. graminearum functions in filamentous fungi, such as the formation of Woronin bodies, which can seal septal pores after cellular wounding (Wanner and Theimer, 1982), metabolism of specific carbon sources (Hynes et al, 2006), and the biosynthesis of secondary metabolites (Brakhage et al, 2004; Meijer et al, 2010; Reverberi et al, 2012). They are involved in virulence (Min et al, 2012) and sexual development (Peraza-Reyes and Berteaux-Lecellier, 2013). The binding of PEX3 and PEX19 is an essential step in the targeting of PMPs to the peroxisomal membrane and absence of either PEX3 or PEX19 results in peroxisome deficiency (Pieuchot and Jedd, 2012)

Methods

Results

Conclusion