Dataset Information

Comparative Genomics of Aspergillus flavus S and L Morphotypes Yield Insights into Niche Adaptation.

ABSTRACT: Aspergillus flavus, the primary causal agent for aflatoxin contamination on crops, consists of isolates with two distinct morphologies: isolates of the S morphotype produce numerous small sclerotia and lower numbers of conidia while isolates of the L morphotype produce fewer large sclerotia and abundant conidia. The morphotypes also differ in aflatoxin production with S isolates consistently producing high concentrations of aflatoxin, whereas L isolates range from atoxigenic to highly toxigenic. The production of abundant sclerotia by the S morphotype suggests adaptation for long-term survival in the soil, whereas the production of abundant conidia by the L morphotype suggests adaptation for aerial dispersal to the phyllosphere. To identify genomic changes that support differential niche adaption, the sequences of three S and three L morphotype isolates were compared. Differences in genome structure and gene content were identified between the morphotypes. A >530 kb inversion between the morphotypes affect a secondary metabolite gene cluster and a cutinase gene. The morphotypes also differed in proteins predicted to be involved in carbon/nitrogen metabolism, iron acquisition, antimicrobial defense, and evasion of host immunity. The S morphotype genomes contained more intact secondary metabolite clusters indicating there is higher selection pressure to maintain secondary metabolism in the soil and that it is not limited to aflatoxin production. The L morphotype genomes were enriched in amino acid transporters, suggesting efficient nitrogen transport may be critical in the nutrient limited phyllosphere. These findings indicate the genomes of the two morphotypes differ beyond developmental genes and have diverged as they adapted to their respective niches.

SUBMITTER: Ohkura M

PROVIDER: S-EPMC6288828 | biostudies-literature | 2018 Dec

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

Comparative Genomics of Aspergillus flavus S and L Morphotypes Yield Insights into Niche Adaptation.

Ohkura Mana M Cotty Peter J PJ Orbach Marc J MJ

G3 (Bethesda, Md.) 20181210 12

Aspergillus flavus, the primary causal agent for aflatoxin contamination on crops, consists of isolates with two distinct morphologies: isolates of the S morphotype produce numerous small sclerotia and lower numbers of conidia while isolates of the L morphotype produce fewer large sclerotia and abundant conidia. The morphotypes also differ in aflatoxin production with S isolates consistently producing high concentrations of aflatoxin, whereas L isolates range from atoxigenic ...[more]

PMID: 30361280

Similar Datasets

Project description:The vascular wilt fungi Verticillium dahliae and V. albo-atrum infect over 200 plant species, causing billions of dollars in annual crop losses. The characteristic wilt symptoms are a result of colonization and proliferation of the pathogens in the xylem vessels, which undergo fluctuations in osmolarity. To gain insights into the mechanisms that confer the organisms' pathogenicity and enable them to proliferate in the unique ecological niche of the plant vascular system, we sequenced the genomes of V. dahliae and V. albo-atrum and compared them to each other, and to the genome of Fusarium oxysporum, another fungal wilt pathogen. Our analyses identified a set of proteins that are shared among all three wilt pathogens, and present in few other fungal species. One of these is a homolog of a bacterial glucosyltransferase that synthesizes virulence-related osmoregulated periplasmic glucans in bacteria. Pathogenicity tests of the corresponding V. dahliae glucosyltransferase gene deletion mutants indicate that the gene is required for full virulence in the Australian tobacco species Nicotiana benthamiana. Compared to other fungi, the two sequenced Verticillium genomes encode more pectin-degrading enzymes and other carbohydrate-active enzymes, suggesting an extraordinary capacity to degrade plant pectin barricades. The high level of synteny between the two Verticillium assemblies highlighted four flexible genomic islands in V. dahliae that are enriched for transposable elements, and contain duplicated genes and genes that are important in signaling/transcriptional regulation and iron/lipid metabolism. Coupled with an enhanced capacity to degrade plant materials, these genomic islands may contribute to the expanded genetic diversity and virulence of V. dahliae, the primary causal agent of Verticillium wilts. Significantly, our study reveals insights into the genetic mechanisms of niche adaptation of fungal wilt pathogens, advances our understanding of the evolution and development of their pathogenesis, and sheds light on potential avenues for the development of novel disease management strategies to combat destructive wilt diseases.

Project description:Aspergillus flavus aflR, a gene encoding a Zn(II)2Cys6 DNA-binding domain, is an important transcriptional regulator of the aflatoxin biosynthesis gene cluster. Our previous results of Gene ontology (GO) analysis for the binding sites of AflR in A. flavus suggest that AflR may play an integrative regulatory role. In this study the ΔaflR and overexpression (OE) strains based on the well-established double-crossover recombinational technique were constructed to investigate the integrative function of the aflR gene in A. flavus. The disruption of aflR severely affected the aflatoxin biosynthetic pathway, resulting in a significant decrease in aflatoxin production. The aflatoxin B1 (AFB1) of the ΔaflR strain was 180 ng/mL and aflatoxin B2 (AFB2) was 2.95 ng/mL on YES medium for 5 days, which was 1/1,000 of that produced by the wild-type strain (WT). In addition, the ΔaflR strain produced relatively sparse conidia and a very small number of sclerotia. On the seventh day, the sclerotia yield on each plate of the WT and OE strains exceeded 1,000, while the sclerotial formation of the ΔaflR strain was not detected until 14 days. However, the biosynthesis of cyclopiazonic acid (CPA) was not affected by aflR gene disruption. Transcriptomic analysis of the ΔaflR strain grown on potato dextrose agar (PDA) plates at 0 h, 24 h, and 72 h showed that expression of clustering genes involved in the biosynthesis of aflatoxin was significantly downregulated. Meanwhile, the ΔaflR strain compared with the WT strain showed significant expression differences in genes involved in spore germination, sclerotial development, and carbohydrate metabolism compared to the WT. The results demonstrated that the A. flavus aflR gene also played a positive role in the fungal growth and development in addition to aflatoxin biosynthesis. IMPORTANCE Past studies of the A. flavus aflR gene and its orthologues in related Aspergillus species were solely focused on their roles in secondary metabolism. In this study, we used the ΔaflR and OE strains to demonstrate the role of aflR in growth and development of A. flavus. For the first time, we confirmed that the ΔaflR strain also was defective in production of conidia and sclerotia, asexual propagules of A. flavus. Our transcriptomic analysis further showed that genes involved in spore germination, sclerotial development, aflatoxin biosynssssthesis, and carbohydrate metabolism exhibited significant differences in the ΔaflR strain compared with the WT strain. Our study indicates that AflR not only plays an important role in regulating aflatoxin synthesis but also in playing a positive role in the conidial formation and sclerotial development in A. flavus. This study reveals the critical and positive role of the aflR gene in fungal growth and development, and provides a theoretical basis for the genetic studies of other aspergilli.

Dataset Information

Comparative Genomics of Aspergillus flavus S and L Morphotypes Yield Insights into Niche Adaptation.

Publications

Comparative Genomics of <i>Aspergillus flavus</i> S and L Morphotypes Yield Insights into Niche Adaptation.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets