The wheat head blight fungus
- NSF-PAR ID:
- Publisher / Repository:
- American Society of Plant Biologists (ASPB)
- Date Published:
- Journal Name:
- Plant Physiology
- Page Range / eLocation ID:
- p. 463-471
- Medium: X
- Sponsoring Org:
- National Science Foundation
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The wheat head blight fungus
Fusarium graminearumhas two highly similar beta‐tubulin genes with overlapping functions during vegetative growth but only TUB1is 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 of TUB1.Deletion of TUB1blocked the late but not initial stages of perithecium formation. Perithecia formed by tub1mutant had limited ascogenous hyphae and failed to develop asci. Silencing of TUB1by MSUD also resulted in defects in ascospore formation. Interestingly, the 3′‐UTR of TUB1was 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 in TUB1conferred tolerance to carbendazim and caused a minor defect in sexual reproduction. Taken together, our data indicate TUB1plays an essential role in ascosporogenesis and sexual‐specific functions of TUB1require stage‐specific RNA processing and Tub1 expression.
Glomeromycotina is a lineage of early diverging fungi that establish arbuscular mycorrhizal (
AM) symbiosis with land plants. Despite their major ecological role, the genetic basis of their obligate mutualism remains largely unknown, hindering our understanding of their evolution and biology.
We compared the genomes of Glomerales (
Rhizophagus irregularis, Rhizophagus diaphanus, Rhizophagus cerebriforme) and Diversisporales ( Gigaspora rosea) species, together with those of saprotrophic Mucoromycota ,to identify gene families and processes associated with these lineages and to understand the molecular underpinning of their symbiotic lifestyle.
Genomic features in Glomeromycotina appear to be very similar with a very high content in transposons and protein‐coding genes, extensive duplications of protein kinase genes, and loss of genes coding for lignocellulose degradation, thiamin biosynthesis and cytosolic fatty acid synthase. Most symbiosis‐related genes in
R. irregularisand G. roseaare specific to Glomeromycotina. We also confirmed that the present species have a homokaryotic genome organisation.
The high interspecific diversity of Glomeromycotina gene repertoires, affecting all known protein domains, as well as symbiosis‐related orphan genes, may explain the known adaptation of Glomeromycotina to a wide range of environmental settings. Our findings contribute to an increasingly detailed portrait of genomic features defining the biology of
The collaborative non‐self‐recognition model for S‐
RNase‐based self‐incompatibility predicts that multiple S‐locus F‐box proteins ( SLFs) produced by pollen of a given S‐haplotype collectively mediate ubiquitination and degradation of all non‐self S‐ RNases, but not self S‐ RNases, in the pollen tube, thereby resulting in cross‐compatible pollination but self‐incompatible pollination. We had previously used pollen extracts containing GFP‐fused S2‐ SLF1 ( SLF1 with an S2‐haplotype) of Petunia inflatafor co‐immunoprecipitation (Co‐ IP) and mass spectrometry ( MS), and identified Pi CUL1‐P (a pollen‐specific Cullin1), Pi SSK1 (a pollen‐specific Skp1‐like protein) and Pi RBX1 (a conventional Rbx1) as components of the SCFS2– SLF1complex. Using pollen extracts containing Pi SSK1: FLAG: GFPfor Co‐ IP/ MS, we identified two additional SLFs ( SLF4 and SLF13) that were assembled into SCFSLFcomplexes. As 17 genes ( SLF to SLF1 ) have been identified in SLF17 S2and S3pollen, here we examined whether all 17 SLFs are assembled into similar complexes and, if so, whether these complexes are unique to SLFs. We modified the previous Co‐ IP/ MSprocedure, including the addition of style extracts from four different S‐genotypes to pollen extracts containing Pi SSK1: FLAG: GFP, to perform four separate experiments. The results taken together show that all 17 SLFs and an SLF‐like protein, SLFLike1 (encoded by an S‐locus‐linked gene), co‐immunoprecipitated with Pi SSK1: FLAG: GFP. Moreover, of the 179 other F‐box proteins predicted by S2and S3pollen transcriptomes, only a pair with 94.9% identity and another pair with 99.7% identity co‐immunoprecipitated with Pi SSK1: FLAG: GFP. These results suggest that SCFSLFcomplexes have evolved specifically to function in self‐incompatibility.
During plant infection, fungi secrete effector proteins in coordination with distinct infection stages. Thus, the success of plant infection is determined by precise control of effector gene expression. We analysed the
PWL2effector gene of the rice blast fungus Magnaporthe oryzaeto understand how effector genes are activated specifically during the early biotrophic stages of rice infection. Here, we used confocal live‐cell imaging of M. oryzaetransformants with various PWL2promoter fragments fused to sensitive green fluorescent protein reporter genes to determine the expression patterns of PWL2at the cellular level, together with quantitative reverse transcription PCR analyses at the tissue level. We found PWL2expression was coupled with sequential biotrophic invasion of rice cells. PWL2expression was induced in the appressorium upon penetration into a living rice cell but greatly declined in the highly branched hyphae when the first‐invaded rice cell was dead. PWL2expression then increased again as the hyphae penetrate into living adjacent cells. The expression of PWL2required fungal penetration into living plant cells of either host rice or nonhost onion. Deletion and mutagenesis experiments further revealed that the tandem repeats in the PWL2promoter contain 12‐base pair sequences required for expression. We conclude that PWL2expression is (a) activated by an unknown signal commonly present in living plant cells, (b) specific to biotrophic stages of fungal infection, and (c) requires 12‐base pair cis‐regulatory sequences in the promoter.