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

Kunlong Yang,Zhenguo Li,Linlin Liang,Xinyi Nie,Shihua Wang,Huahui Lan,Shimuye Kalayu Yirga,Zhenhong Zhuang,Feng Zhang,Peili Gao,Fanlei Ran,Yinghang Liu

doi:10.1038/srep23259

Kunlong Yang, Zhenguo Li + Show 10 more

Open Access

https://doi.org/10.1038/srep23259

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Journal: Scientific Reports	Publication Date: Mar 16, 2016
Citations: 91	License type: CC BY 4.0

Affiliation: Fujian Agriculture and Forestry University

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.

Highlights

The Aspergillus genus is a large, worldwide family of fungi with more than 185 known species, among which A. flavus is the most economically important because it contaminates seed crops and food-stuffs with the toxic and carcinogenic secondary metabolite, aflatoxin (AF)[14,15,16]
In A. flavus, the existence of DNA methylation is controversial, our former study has shown that use of the DMT inhibitor 5-azacytidine resulted in decreased AF production and concurrent morphological changes[15], suggesting that DNA methylation or DMTs possibly play roles in AF metabolism and A. flavus development
Dnmt[1], which plays a vital role in maintaining DNA methylation, has five conserved domains, namely a DMAP1-binding domain, a DNA-methyltransferase

Summary

Introduction

The Aspergillus genus is a large, worldwide family of fungi with more than 185 known species, among which A. flavus is the most economically important because it contaminates seed crops and food-stuffs with the toxic and carcinogenic secondary metabolite, aflatoxin (AF)[14,15,16] Ingestion of such contaminated food poses a significant threat to human and animal health because of its hepatotoxicity and immunotoxicity[15,17,18]. In A. flavus, the existence of DNA methylation is controversial, our former study has shown that use of the DMT inhibitor 5-azacytidine resulted in decreased AF production and concurrent morphological changes[15], suggesting that DNA methylation or DMTs possibly play roles in AF metabolism and A. flavus development This is surprising, because neither widespread DNA methylation nor active DMTs have been identified in A. flavus[11]. Inactivation of dmtA inhibited AF biosynthesis and conidiation, and resulted in a change of seed infection

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