title: Bisulfite sequencing reveals that Aspergillus flavus holds a hollow in DNA methylation.
abstract: Aspergillus flavus first gained scientific attention for its production of aflatoxin. The underlying regulation of aflatoxin biosynthesis has been serving as a theoretical model for biosynthesis of other microbial secondary metabolites. Nevertheless, for several decades, the DNA methylation status, one of the important epigenomic modifications involved in gene regulation, in A. flavus remains to be controversial. Here, we applied bisulfite sequencing in conjunction with a biological replicate strategy to investigate the DNA methylation profiling of A. flavus genome. Both the bisulfite sequencing data and the methylome comparisons with other fungi confirm that the DNA methylation level of this fungus is negligible. Further investigation into the DNA methyltransferase of Aspergillus uncovers its close relationship with RID-like enzymes as well as its divergence with the methyltransferase of species with validated DNA methylation. The lack of repeat contents of the A. flavus' genome and the high RIP-index of the small amount of remanent repeat potentially support our speculation that DNA methylation may be absent in A. flavus or that it may possess de novo DNA methylation which occurs very transiently during the obscure sexual stage of this fungal species. This work contributes to our understanding on the DNA methylation status of A. flavus, as well as reinforces our views on the DNA methylation in fungal species. In addition, our strategy of applying bisulfite sequencing to DNA methylation detection in species with low DNA methylation may serve as a reference for later scientific investigations in other hypomethylated species.
authors.affiliation: MOE Key Laboratory of Aquatic Product Safety, School of Life Sciences, Sun Yat-sen University, Guangzhou, China.
authors.forename: Si-Yang
authors.initials: SY
authors.lastname: Liu
authors.forename: Jian-Qing
authors.initials: JQ
authors.lastname: Lin
authors.forename: Hong-Long
authors.initials: HL
authors.lastname: Wu
authors.forename: Cheng-Cheng
authors.initials: CC
authors.lastname: Wang
authors.forename: Shu-Jia
authors.initials: SJ
authors.lastname: Huang
authors.forename: Yan-Feng
authors.initials: YF
authors.lastname: Luo
authors.forename: Ji-Hua
authors.initials: JH
authors.lastname: Sun
authors.forename: Jian-Xiang
authors.initials: JX
authors.lastname: Zhou
authors.forename: Shu-Jing
authors.initials: SJ
authors.lastname: Yan
authors.forename: Jian-Guo
authors.initials: JG
authors.lastname: He
authors.forename: Jun
authors.initials: J
authors.lastname: Wang
authors.forename: Zhu-Mei
authors.initials: ZM
authors.lastname: He
mesh_terms: D001231:Aspergillus flavus / Q000235:genetics*; D019175:DNA Methylation / Q000235:genetics*; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics*; D017422:Sequence Analysis, DNA; D013447:Sulfites / Q000737:chemistry
chemical_list: D004271:DNA, Fungal; D013447:Sulfites; C042345:hydrogen sulfite