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Ascospores generated during sexual reproduction are the primary inoculum for the wheat scab fungus Fusarium graminearum. Purine metabolism is known to play important roles in fungal pathogens but its lifecycle stage-specific regulation is unclear. By characterizing the genes involved in purine de novo and salvage biosynthesis pathways, we showed that de novo syntheses of inosine, adenosine and guanosine monophosphates (IMP, AMP and GMP) are important for vegetative growth, sexual/asexual reproduction, and infectious growth, whereas purine salvage synthesis is dispensable for these stages in F. graminearum. Addition of GMP rescued the defects of the Fgimd1 mutant in vegetative growth and conidiation but not sexual reproduction, whereas addition of AMP rescued all of these defects of the Fgade12 mutant, suggesting that the function of de novo synthesis of GMP rather than AMP is distinct in sexual stages. Moreover, Acd1, an ortholog of AMP deaminase, is dispensable for growth but essential for ascosporogenesis and pathogenesis, suggesting that AMP catabolism has stage-specific functions during sexual reproduction and infectious growth. The expression of almost all the genes involved in de novo purine synthesis is downregulated during sexual reproduction and infectious growth relative to vegetative growth. This study revealed that F. graminearum has stage-specific regulation of purine metabolism during infectious growth and sexual reproduction.
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The meiosis‐specific APC activator FgAMA1 is dispensable for meiosis but important for ascosporogenesis in Fusarium graminearum
Summary Ascospores are the primary inoculum inFusarium graminearum. Interestingly, 70 of its genes have premature stop codons (PSC) and require A‐to‐I editing during sexual reproduction to encode full‐length proteins, including the ortholog of yeast Ama1, a meiosis‐specific activator of APC/C. In this study, we characterized the function ofFgAMA1and its PSC editing.FgAMA1was specifically expressed during sexual reproduction. TheFgama1mutant was normal in growth and perithecium formation but defective in ascospogenesis. Instead of forming four‐celled, uninucleate ascospores,Fgama1mutant produced oval, single‐celled, binucleated ascospores by selfing. Some mutant ascospores began to bud and underwent additional mitosis inside asci. Expression of the wild‐type or editedFgAMA1but not the uneditable allele complementedFgama1. In theFgama1xmat‐1‐1outcross, over 60% of the asci had eightFgama1or intermediate (elongated but single‐celled) ascospores, suggesting efficient meiotic silencing of unpairedFgAMA1. Deletion ofFgPAL1, one of the genes upregulated inFgama1also resulted in defects in ascospore morphology and budding. Overall, our results showed thatFgAMA1is dispensable for meiosis but important for ascospore formation and discharge. InF. graminearum, whereas some of its targets are functional during meiosis, FgAma1 may target other proteins that function after spore delimitation.
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- Award ID(s):
- 1758434
- PAR ID:
- 10088415
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Molecular Microbiology
- Volume:
- 111
- Issue:
- 5
- ISSN:
- 0950-382X
- Page Range / eLocation ID:
- p. 1245-1262
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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