The wheat head blight fungus
Ascospores are the primary inoculum in
- Award ID(s):
- 1758434
- NSF-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
More Like this
-
more » « less
Summary Fusarium graminearum has two highly similar beta‐tubulin genes with overlapping functions during vegetative growth but onlyTUB1 is important for sexual reproduction. To better understand their functional divergence during ascosporogenesis, in this study we characterized the sequence elements important for stage‐specific functions ofTUB1. Deletion ofTUB1 blocked the late but not initial stages of perithecium formation. Perithecia formed bytub1 mutant had limited ascogenous hyphae and failed to develop asci. Silencing ofTUB1 by MSUD also resulted in defects in ascospore formation. Interestingly, the 3′‐UTR ofTUB1 was dispensable for growth but essential for its function during sexual reproduction. RIP mutations that specifically affected Tub1 functions during sexual reproduction also were identified in two ascospore progeny. Furthermore, site‐directed mutagenesis showed that whereas the non‐editable mutations at three A‐to‐I RNA editing sites had no effects, the N347D (not T362D or I368V) edited mutation affected ascospore development. In addition, the F167Y, but not E198K or F200Y, mutation inTUB1 conferred tolerance to carbendazim and caused a minor defect in sexual reproduction. Taken together, our data indicateTUB1 plays an essential role in ascosporogenesis and sexual‐specific functions ofTUB1 require stage‐specific RNA processing and Tub1 expression. -
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.more » « less
-
Goldman, Gustavo H. (Ed.)ABSTRACT Gene expression divergence through evolutionary processes is thought to be important for achieving programmed development in multicellular organisms. To test this premise in filamentous fungi, we investigated transcriptional profiles of 3,942 single-copy orthologous genes (SCOGs) in five related sordariomycete species that have morphologically diverged in the formation of their flask-shaped perithecia. We compared expression of the SCOGs to inferred gene expression levels of the most recent common ancestor of the five species, ranking genes from their largest increases to smallest increases in expression during perithecial development in each of the five species. We found that a large proportion of the genes that exhibited evolved increases in gene expression were important for normal perithecial development in Fusarium graminearum . Many of these genes were previously uncharacterized, encoding hypothetical proteins without any known functional protein domains. Interestingly, the developmental stages during which aberrant knockout phenotypes appeared largely coincided with the elevated expression of the deleted genes. In addition, we identified novel genes that affected normal perithecial development in Magnaporthe oryzae and Neurospora crassa , which were functionally and transcriptionally diverged from the orthologous counterparts in F. graminearum . Furthermore, comparative analysis of developmental transcriptomes and phylostratigraphic analysis suggested that genes encoding hypothetical proteins are generally young and transcriptionally divergent between related species. This study provides tangible evidence of shifts in gene expression that led to acquisition of novel function of orthologous genes in each lineage and demonstrates that several genes with hypothetical function are crucial for shaping multicellular fruiting bodies. IMPORTANCE The fungal class Sordariomycetes includes numerous important plant and animal pathogens. It also provides model systems for studying fungal fruiting body development, as its members develop fruiting bodies with a few well-characterized tissue types on common growth media and have rich genomic resources that enable comparative and functional analyses. To understand transcriptional divergence of key developmental genes between five related sordariomycete fungi, we performed targeted knockouts of genes inferred to have evolved significant upward shifts in expression. We found that many previously uncharacterized genes play indispensable roles at different stages of fruiting body development, which have undergone transcriptional activation in specific lineages. These novel genes are predicted to be phylogenetically young and tend to be involved in lineage- or species-specific function. Transcriptional activation of genes with unknown function seems to be more frequent than ever thought, which may be crucial for rapid adaption to changing environments for successful sexual reproduction.more » « less
-
Salz, H (Ed.)more » « less
Abstract Meiosis is usually described as 4 essential and sequential processes: (1) homolog pairing; (2) synapsis, mediated by the synaptonemal complex; (3) crossing over; and (4) segregation. In this canonical model, the maturation of crossovers into chiasmata plays a vital role in holding homologs together and ensuring their segregation at the first meiotic division. However, Lepidoptera (moths and butterflies) undergo 3 distinct meiotic processes, only one of which is canonical. Lepidoptera males utilize 2 meiotic processes: canonical meiosis that produces nucleated fertile sperm, and a noncanonical meiosis that produces anucleated nonfertile sperm which are nonetheless essential for reproduction. Lepidoptera females, which carry heteromorphic sex chromosomes, undergo a completely achiasmate (lacking crossovers) meiosis, thereby requiring an alternative mechanism to ensure proper homolog segregation. Here, we report that the development of a molecular cell biology toolkit designed to properly analyze features of meiosis, including the synaptonemal complex structure and function, in the silkworm Bombyx mori. In addition to standard homology searches to identify Bombyx orthologs of known synaptonemal complex encoding genes, we developed an ortholog discovery app (Shinyapp) to identify Bombyx orthologs of proteins involved in several meiotic processes. We used this information to clone genes expressed in the testes and then created antibodies against their protein products. We used the antibodies to confirm the localization of these proteins in normal male spermatocytes, as well as using in vitro assays to confirm orthologous interactions. The development of this toolkit will facilitate further study of the unique meiotic processes that characterize meiosis in Lepidoptera.
-
Lin, Xiaorong (Ed.)ABSTRACT Adenosine-to-inosine (A-to-I) RNA editing independent of adenosine deaminase acting on RNA (ADAR) enzymes was discovered in fungi recently, and shown to be crucial for sexual reproduction. However, the underlying mechanism for editing is unknown. Here, we combine genome-wide comparisons, proof-of-concept experiments, and machine learning to decipher cis -regulatory elements of A-to-I editing in Fusarium graminearum . We identified plenty of RNA primary sequences and secondary structural features that affect editing specificity and efficiency. Although hairpin loop structures contribute importantly to editing, unlike in animals, the primary sequences have more profound influences on editing than secondary structures. Nucleotide preferences at adjacent positions of editing sites are the most important features, especially preferences at the −1 position. Unexpectedly, besides the number of positions with preferred nucleotides, the combination of preferred nucleotides with depleted ones at different positions are also important for editing. Some cis -sequence features have distinct importance for editing specificity and efficiency. Machine learning models built from diverse sequence and secondary structural features can accurately predict genome-wide editing sites but not editing levels, indicating that the cis -regulatory principle of editing efficiency is more complex than that of editing specificity. Nevertheless, our model interpretation provides insights into the quantitative contribution of each feature to the prediction of both editing sites and levels. We found that efficient editing of FG3G34330 transcripts depended on the full-length RNA molecule, suggesting that additional RNA structural elements may also contribute to editing efficiency. Our work uncovers multidimensional cis -regulatory elements important for A-to-I RNA editing in F. graminearum , helping to elucidate the fungal editing mechanism. IMPORTANCE A-to-I RNA editing is a new epigenetic phenomenon that is crucial for sexual reproduction in fungi. Deciphering cis -regulatory elements of A-to-I RNA editing can help us elucidate the editing mechanism and develop a model that accurately predicts RNA editing. In this study, we discovered multiple RNA sequence and secondary structure features important for A-to-I editing in Fusarium graminearum . We also identified the cis -sequence features with distinct importance for editing specificity and efficiency. The potential importance of full-length RNA molecules for editing efficiency is also revealed. This study represents the first comprehensive investigation of the cis -regulatory principles of A-to-I RNA editing in fungi.more » « less
