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Protein phosphatase 2A regulatory subunits perform distinct functional roles in the maize pathogen Fusarium verticillioides.

ABSTRACT: Fusarium verticillioides is a pathogen of maize causing ear rot and stalk rot. The fungus also produces fumonisins, a group of mycotoxins linked to disorders in animals and humans. A cluster of genes, designated FUM genes, plays a key role in the synthesis of fumonisins. However, our understanding of the regulatory mechanism of fumonisin biosynthesis is still incomplete. We have demonstrated previously that Cpp1, a protein phosphatase type 2A (PP2A) catalytic subunit, negatively regulates fumonisin production and is involved in cell shape maintenance. In general, three PP2A subunits, structural A, regulatory B and catalytic C, make up a heterotrimer complex to perform regulatory functions. Significantly, we identified two PP2A regulatory subunits in the F.?verticillioides genome, Ppr1 and Ppr2, which are homologous to Saccharomyces cerevisiae?Cdc55 and Rts1, respectively. In this study, we hypothesized that Ppr1 and Ppr2 are involved in the regulation of fumonisin biosynthesis and/or cell development in F.?verticillioides, and generated a series of mutants to determine the functional role of Ppr1 and Ppr2. The PPR1 deletion strain (?ppr1) resulted in drastic growth defects, but increased microconidia production. The PPR2 deletion mutant strain (?ppr2) showed elevated fumonisin production, similar to the ?cpp1 strain. Germinating ?ppr1 conidia formed abnormally swollen cells with a central septation site, whereas ?ppr2 showed early hyphal branching during conidia germination. A kernel rot assay showed that the mutants were slow to colonize kernels, but this is probably a result of growth defects rather than a virulence defect. Results from this study suggest that two PP2A regulatory subunits in F.?verticillioides carry out distinct roles in the regulation of fumonisin biosynthesis and fungal development.

SUBMITTER: Shin JH

PROVIDER: S-EPMC6638791 | biostudies-literature | 2013 Jun

REPOSITORIES: biostudies-literature

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Protein phosphatase 2A regulatory subunits perform distinct functional roles in the maize pathogen Fusarium verticillioides.

Shin Joon-Hee JH Kim Jung-Eun JE Malapi-Wight Martha M Choi Yoon-E YE Shaw Brian D BD Shim Won-Bo WB

Molecular plant pathology 20130303 5

Fusarium verticillioides is a pathogen of maize causing ear rot and stalk rot. The fungus also produces fumonisins, a group of mycotoxins linked to disorders in animals and humans. A cluster of genes, designated FUM genes, plays a key role in the synthesis of fumonisins. However, our understanding of the regulatory mechanism of fumonisin biosynthesis is still incomplete. We have demonstrated previously that Cpp1, a protein phosphatase type 2A (PP2A) catalytic subunit, negatively regulates fumoni ...[more]

PMID: 23452277

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Project description:GBB1, a heterotrimeric G-protein β-subunit gene, was shown to be a key regulator of fumonisin B(1) (FB(1) ) biosynthesis in the maize pathogen Fusarium verticillioides. In this study, we performed functional analyses of genes that encode putative RGS (regulators of G-protein signalling) proteins and PhLPs (phosducin-like proteins) in F. verticillioides. These proteins are known to regulate heterotrimeric G-protein activity by altering the intrinsic guanosine triphosphatase (GTPase) activity, which, in turn, influences the signalling mechanisms that control fungal growth, virulence and secondary metabolism. Our aim was to isolate and characterize gene(s) that are under the transcriptional control of GBB1, and to test the hypothesis that these genes are directly associated with FB(1) regulation and fungal development in F. verticillioides on maize kernels. We first identified eight genes (two PhLPs and six RGSs) in the F. verticillioides genome, and a subsequent transcriptional expression study revealed that three RGS genes were up-regulated in the gbb1 deletion (Δgbb1) mutant and one RGS gene was up-regulated in the wild-type. To characterize their function, we generated knockout mutants using a homologous recombination strategy. When grown on autoclaved nonviable kernels, two mutants (ΔflbA2 and ΔrgsB) produced significantly higher levels of FB(1) compared with the wild-type progenitor, suggesting that the two mutated genes are negative regulators of FB(1) biosynthesis. ΔflbA2 also showed a severe curly conidia germination pattern, which was contradictory to that observed in the Δgbb1 strain. Strikingly, when these mutants were grown on live maize kernels, we observed contrasting FB(1) and conidiation phenotypes in fungal mutants, which strongly suggests that these G-protein regulators have an impact on how F. verticillioides responds to host/environmental factors. Our data also provide evidence that fungal G-protein signalling is important for modulating the ethylene biosynthetic pathway in maize kernels.

Dataset Information

Protein phosphatase 2A regulatory subunits perform distinct functional roles in the maize pathogen Fusarium verticillioides.

Publications

Protein phosphatase 2A regulatory subunits perform distinct functional roles in the maize pathogen Fusarium verticillioides.

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