Linz John E, Wee Josephine, Roze Ludmila V
Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan, USA Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA Center for Integrative Toxicology, Michigan State University, East Lansing, Michigan, USA
Department of Food Science and Human Nutrition, Michigan State University, East Lansing, Michigan, USA.
Eukaryot Cell. 2014 Aug;13(8):1113-23. doi: 10.1128/EC.00108-14. Epub 2014 Jun 20.
The filamentous fungi Aspergillus parasiticus and Aspergillus flavus produce the carcinogenic secondary metabolite aflatoxin on susceptible crops. These species differ in the quantity of aflatoxins B1, B2, G1, and G2 produced in culture, in the ability to produce the mycotoxin cyclopiazonic acid, and in morphology of mycelia and conidiospores. To understand the genetic basis for differences in biochemistry and morphology, we conducted next-generation sequence (NGS) analysis of the A. parasiticus strain SU-1 genome and comparative gene expression (RNA sequence analysis [RNA Seq]) analysis of A. parasiticus SU-1 and A. flavus strain NRRL 3357 (3357) grown under aflatoxin-inducing and -noninducing culture conditions. Although A. parasiticus SU-1 and A. flavus 3357 are highly similar in genome structure and gene organization, we observed differences in the presence of specific mycotoxin gene clusters and differential expression of specific mycotoxin genes and gene clusters that help explain differences in the type and quantity of mycotoxins synthesized. Using computer-aided analysis of secondary metabolite clusters (antiSMASH), we demonstrated that A. parasiticus SU-1 and A. flavus 3357 may carry up to 93 secondary metabolite gene clusters, and surprisingly, up to 10% of the genome appears to be dedicated to secondary metabolite synthesis. The data also suggest that fungus-specific zinc binuclear cluster (C6) transcription factors play an important role in regulation of secondary metabolite cluster expression. Finally, we identified uniquely expressed genes in A. parasiticus SU-1 that encode C6 transcription factors and genes involved in secondary metabolism and stress response/cellular defense. Future work will focus on these differentially expressed A. parasiticus SU-1 loci to reveal their role in determining distinct species characteristics.
寄生曲霉和黄曲霉这两种丝状真菌会在易感作物上产生致癌的次生代谢产物黄曲霉毒素。这两个菌种在培养物中产生的黄曲霉毒素B1、B2、G1和G2的量、产生霉菌毒素环匹阿尼酸的能力以及菌丝体和分生孢子的形态方面存在差异。为了了解生物化学和形态差异的遗传基础,我们对寄生曲霉SU-1菌株的基因组进行了二代测序(NGS)分析,并对在黄曲霉毒素诱导和非诱导培养条件下生长的寄生曲霉SU-1和黄曲霉NRRL 3357(3357)菌株进行了比较基因表达(RNA序列分析[RNA Seq])分析。尽管寄生曲霉SU-1和黄曲霉3357在基因组结构和基因组织上高度相似,但我们观察到特定霉菌毒素基因簇的存在以及特定霉菌毒素基因和基因簇的差异表达,这些有助于解释合成的霉菌毒素的类型和数量差异。通过对次生代谢产物簇的计算机辅助分析(antiSMASH),我们证明寄生曲霉SU-1和黄曲霉3357可能携带多达93个次生代谢产物基因簇,令人惊讶的是,高达10%的基因组似乎专门用于次生代谢产物的合成。数据还表明,真菌特异性锌双核簇(C6)转录因子在次生代谢产物簇表达的调控中起重要作用。最后,我们在寄生曲霉SU-1中鉴定出了独特表达的基因,这些基因编码C6转录因子以及参与次生代谢和应激反应/细胞防御的基因。未来的工作将集中在这些差异表达的寄生曲霉SU-1基因座上,以揭示它们在决定不同物种特征中的作用。