Flippases play specific but distinct roles in the development, pathogenicity, and secondary metabolism of Fusarium graminearum

Abstract

The membrane trafficking system is important for compartmentalization of the biosynthesis pathway and secretion of deoxynivalenol (DON) mycotoxin (a virulence factor) in Fusarium graminearum. Flippases are transmembrane lipid transporters and mediate a number of essential physiological steps of membrane trafficking, including vesicle budding, charging, and protein diffusion within the membrane. However, the roles of flippases in secondary metabolism remain unknown in filamentous fungi. Herein, we identified five flippases (FgDnfA, FgDnfB, FgDnfC1, FgDnfC2, and FgDnfD) in F. graminearum and established their specific and redundant functions in the development and pathogenicity of this phytopathogenic fungus. Our results demonstrate that FgDnfA is critical for normal vegetative growth while the other flippases are dispensable. FgDnfA and FgDnfD were found crucial for the fungal pathogenesis, and a remarkable reduction in DON production was observed in ΔFgDNFA and ΔFgDNFD. Deletion of the FgDNFB gene increased DON production to about 30 times that produced by the wild type. Further analysis showed that FgDnfA and FgDnfD have positive roles in the regulation of trichothecene (TRI) genes (TRI1, TRI4, TRI5, TRI6, TRI12, and TRI101) expression and toxisome reorganization, while FgDnfB acts as a negative regulator of DON synthesis. In addition, FgDnfB and FgDnfD have redundant functions in the regulation of phosphatidylcholine transport, and double deletion of FgDNFB and FgDNFD showed serious defects in fungal development, DON synthesis, and virulence. Collectively, our findings reveal the distinct and specific functions of flippase family members in F. graminearum and principally demonstrate that FgDnfA, FgDnfD, and FgDnfB have specific spatiotemporal roles during toxisome biogenesis.

Toxicity and action mechanisms of silver nanoparticles against the mycotoxin-producing fungus Fusarium graminearum

“…Among the six AgNP-induced FgTRI genes, FgTRI1 encodes a calonectrin oxygenase FgTri1, which catalyzes the late step in DON biosynthesis and is delivered to the toxisome under DON induction conditions. Therefore, the formation of toxisomes can be reflected by FgTri1, which shows a positive correlation with DON production [42] . To characterize the subcellular localization of FgTri1 under AgNP treatment, FgTRI1-GFP was introduced into the FgTri1 mutant ΔFgTri1 to obtain FgTri1-GFP expressing strain (ΔFgTri1::FgTri1-GFP) for the toxisome induction assay.…”

“…DON is the primary mycotoxin produced by F. graminearum during pathogenesis, and its biosynthesis is regulated by 15 trichothecene biosynthesis genes ( FgTRI s) [42] . Owing to the threat of DON to human and animal health, the control efficiency of DON contamination is considered a critical indicator to evaluate and apply fungicides for the management of FHB [43] .…”

A Putative P-Type ATPase Regulates the Secretion of Hydrolytic Enzymes, Phospholipid Transport, Morphogenesis, and Pathogenesis in Phytophthora capsici

“…Also, double gene deletion of DNFA and DNFB or DNFC and DNFD is lethal, indicating that flippases also play a different role in the vegetative growth in A. nidulans ( Schultzhaus et al, 2015 , 2019 ). In the plant pathogenic fungi F. graminearum , except for FgDNFA , the other flippases, including FgDNFB (homolog of DRS2 ), are not critical for vegetative growth ( Yun et al, 2020 ). Similarly, the loss of two flippase genes MgPDE1 , and MgAPT2 (homolog gene of DRS2 ), had no adverse influence on the vegetative growth of M. grisea.…”

“…Previous studies have shown that AnDnfA and AnDnfB play a pivotal role in the asymmetric distribution of phosphatidylserine in the phytopathogenic fungus A. nidulans ( Schultzhaus et al, 2015 ). Recently, Yun et al (2020) found that FgDnfB and FgDnfD are involved in the transport of phosphatidylcholine. Our findings showed that P4 ATPase PcApt1 specifically transports PS rather than PE and PC in P. capsici .…”

“…In Fusarium graminearum , recent studies have revealed that the flippases are involved in vegetative growth, asexual and sexual reproduction, and pathogenesis. Moreover, individual flippase plays distinct roles in regulating of DON biosynthesis in F. graminearum ( Li et al, 2019 ; Zhang et al, 2019 ; Yun et al, 2020 ). However, the functions of flippases in vegetative growth, sporulation, and virulence of oomycetes, including P. capsici , remain unknown.…”