The Small GTPase FgRab1 Plays Indispensable Roles in the Vegetative Growth, Vesicle Fusion, Autophagy and Pathogenicity of Fusarium graminearum.

Yanping Yuan,Jingjing Li,Huawei Zheng,Chengdong Yang,Jie Zhou,Meiru Zhang,Xin Chen,Zonghua Wang,Wenhui Zheng,Yakubu Saddeeq Abubakar

doi:10.3390/ijms23020895

Abstract

Rab GTPases are key regulators of membrane and intracellular vesicle transports. However, the biological functions of FgRab1 are still unclear in the devastating wheat pathogen Fusarium graminearum. In this study, we generated constitutively active (CA) and dominant-negative (DN) forms of FgRAB1 from the wild-type PH-1 background for functional analyses. Phenotypic analyses of these mutants showed that FgRab1 is important for vegetative growth, cell wall integrity and hyphal branching. Compared to the PH-1 strain, the number of spores produced by the Fgrab1DN strain was significantly reduced, with obviously abnormal conidial morphology. The number of septa in the conidia of the Fgrab1DN mutant was fewer than that observed in the PH-1 conidia. Fgrab1DN was dramatically reduced in its ability to cause Fusarium head blight symptoms on wheat heads. GFP-FgRab1 was observed to partly localize to the Golgi apparatus, endoplasmic reticulum and Spitzenkörper. Furthermore, we found that FgRab1 inactivation blocks not only the transport of the v-SNARE protein FgSnc1 from the Golgi to the plasma membrane but also the fusion of endocytic vesicles with their target membranes and general autophagy. In summary, our results indicate that FgRab1 plays vital roles in vegetative growth, conidiogenesis, pathogenicity, autophagy, vesicle fusion and trafficking in F. graminearum.

Highlights

Ras related in brain (Rab) GTPases make up the largest group of the small GTPase family and function as molecular switches in the regulation of intracellular membrane trafficking in all eukaryotic cells [1,2,3,4]
We found that the growth of the Fgrab1DN strain was reduced by approximately 77% compared to the wild-type strain, while mycelialstrain growth the was only slightly
Fgrab1DN infection on wheat heads were significantly lower than those observed due to PH-1 and Fgrab1CA infections. These results indicate that FgRab1 is required for normal pathogenicity of F. graminearum

Summary

Introduction

Ras related in brain (Rab) GTPases make up the largest group of the small GTPase family (called Ypt proteins in yeast) and function as molecular switches in the regulation of intracellular membrane trafficking in all eukaryotic cells [1,2,3,4]. Rab GTPases alternate between active GTP-bound and inactive GDP-bound states, which are facilitated by guanine nucleotide exchange factors (GEFs) and GTPase-activating proteins (GAPs), respectively [4]. Rab GTPases have a conserved GTP/GDP core and hydrolysis domain with highly conserved motifs, such as G1 (Walker A/P-loop; GxxxxG K[S/T]), which is implicated in the binding of the β- and γ-phosphate groups of nucleotides [5,6]. Ypt/Rab protein families is stable from 7 to 12 [4,7,8], of which Rab5/Ypt, Rab7/Ypt and

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Results

Conclusion