The DmtA methyltransferase contributes to Aspergillus flavus conidiation, sclerotial production, aflatoxin biosynthesis and virulence

Abstract

DNA methylation is essential for epigenetic regulation of gene transcription and development in many animals, plants and fungi. We investigated whether DNA methylation plays a role in the development and secondary metabolism of Aspergillus flavus, identified the DmtA methyltransferase from A. flavus, and produced a dmtA knock-out mutant by replacing the dmtA coding sequence with the pyrG selectable marker. The A. flavus dmtA null mutant lines produced white fluffy mycelium in liquid medium, and displayed a slightly flavescent conidial pigmentation compared with the normal yellow of the wild-type strain when grown on agar. The ΔdmtA lines exhibited decreased conidiation and aflatoxin (AF) biosynthesis, compared with the wild-type line, suggesting that the DmtA knock-out affected the transcriptional level of genes in the AF cluster. In particular, sclerotia development and host colonization were altered in the dmtA null mutants. Green fluorescent protein tagging at the C-terminus of DmtA showed that DmtA localized to the nucleus and cytoplasm. DNA methylation content measurements in the dmtA mutants revealed no widespread DNA methylation in the mutants or wild-type lines. Thus, our findings suggest that DmtA, apart from being a C-5 cytosine methyltransferase in A. flavus, contributes to asexual development, aflatoxin biosynthesis, sclerotial production and virulence.

Contribution of ATPase copper transporters in animal but not plant virulence of the crossover pathogen Aspergillus flavus

“…Aspergillus flavus gene deletion and transformation experiments were conducted following previously described protocols [51]. For the disruption of crpA, crpB and aceA , a homologous recombination strategy was used to replace each gene with A. flavus argB in the parental strain TJES20.1 and TXZ21.3 strain protoplasts.…”

Aflatoxins: biosynthesis, prevention and eradication

“…The dmtA mutants deficient in DNA methyltransferase exhibited decreased asexual reproduction and aflatoxin biosynthesis in comparison with the wild-type strain A. flavus, suggesting that the dmtA knockout affected the transcriptional level of genes in the aflatoxin cluster. Moreover, dmtA deletion induced such changes in seed infection, which resulted in more conidia (asexual reproduction cells) formation in crop seeds in comparison to the wildtype strain (Yang et al, 2016). The asexual development and AF production were regulated also by the transcription factor NsdC.…”

“…Other genes, non-coded by the aflatoxin gene cluster, have been shown to be involved in regulation of the aflatoxin gene expression (Table 2). Global regulators LaeA and VeA positively regulate aflatoxin production (Yang et al, 2016). Deletion of veA in A. flavus and A. parasiticus strains caused disruption in aflatoxin production.…”

“…(Gilbert et al, 2016) dmtA DmtA, a putative C-5 cytosine methyltransferase, is essential for conidiation and AF metabolism in A. flavus. (Yang et al, 2016) rtfA RtfA modulates expression of the global regulators such as veA, laeA and nsdC possibly through an as of yet uncharacterized role in epigenetic modification of chromatin. (Lohmar et al, 2016) rmtA RmtA regulates secondary metabolism, specifically AF biosynthesis, as well as in developmental processes, affecting conidiation and production of sclerotia.…”

Effects of Aflatoxin-Contaminated Feed on Immunological Parameters of Common Carp (Cyprinus Carpio)

“…Aflatoxins are secondary metabolites of certain mold strains including Aspergillus flavus and A. parasiticus which hurt humans and animals by DNA degradation [2] and epigenetic alterations [3], lipid peroxidation [4], disturbance in biochemical processes [5], tumorigenesis and hypotoxicity [6]; [4]. Disturbance in the antigen presenting capacity of dendritic cells [7], alterations in inflammatory responses [8], a reduction in cytokinin synthesis [9], changes in the activity level of macrophages and neutrophils, lymphocytes disturbance, and reduced effectiveness of vaccination [10] are among changes observed in the immune system of organisms treated with aflatoxins.…”