Comparative genomic and transcriptomic analyses of the Fuzhuan brick tea-fermentation fungus Aspergillus cristatus.
Aspergillus cristatus is the dominant fungus involved in the fermentation of Chinese Fuzhuan brick tea. Aspergillus cristatus is a homothallic fungus that undergoes a sexual stage without asexual conidiation when cultured in hypotonic medium. The asexual stage is induced by a high salt concentration, which completely inhibits sexual development. The taxon is therefore appropriate for investigating the mechanisms of asexual and sexual reproduction in fungi. In this study, de novo genome sequencing and analysis of transcriptomes during culture under high- and low-osmolarity conditions were performed. These analyses facilitated investigation of the evolution of mating-type genes, which determine the mode of sexual reproduction, in A. cristatus, the response of the high-osmolarity glycerol (HOG) pathway to osmotic stimulation, and the detection of mycotoxins and evaluation of the relationship with the location of the encoding genes.



The A. cristatus genome comprised 27.9 Mb and included 68 scaffolds, from which 10,136 protein-coding gene models were predicted. A phylogenetic analysis suggested a considerable phylogenetic distance between A. cristatus and A. nidulans. Comparison of the mating-type gene loci among Aspergillus species indicated that the mode in A. cristatus differs from those in other Aspergillus species. The components of the HOG pathway were conserved in the genome of A. cristatus. Differential gene expression analysis in A. cristatus using RNA-Seq demonstrated that the expression of most genes in the HOG pathway was unaffected by osmotic pressure. No gene clusters associated with the production of carcinogens were detected.



A model of the mating-type locus in A. cristatus is reported for the first time. Aspergillus cristatus has evolved various mechanisms to cope with high osmotic stress. As a fungus associated with Fuzhuan tea, it is considered to be safe under low- and high-osmolarity conditions.
College of Agriculture, Guizhou University, Guiyang, Guizhou, 550025, China.|Guizhou Key Laboratory of Agricultural Biotechnology, Guiyang, Guizhou, 550006, China.|College of Life and Science, Guizhou University, Guiyang, Guizhou, 550025, China.
Yongyi
Y
Ge
Guizhou Key Laboratory of Agricultural Biotechnology, Guiyang, Guizhou, 550006, China.|Guizhou Institute of Biotechnology, Guiyang, Guizhou, 550006, China.
Yuchen
Y
Wang
Guizhou Key Laboratory of Agricultural Biotechnology, Guiyang, Guizhou, 550006, China.|Guizhou Institute of Biotechnology, Guiyang, Guizhou, 550006, China.
YongXiang
Y
Liu
Guizhou Key Laboratory of Agricultural Biotechnology, Guiyang, Guizhou, 550006, China.|Guizhou Institute of Biotechnology, Guiyang, Guizhou, 550006, China.
Yumei
Y
Tan
College of Agriculture, Guizhou University, Guiyang, Guizhou, 550025, China.|Guizhou Key Laboratory of Agricultural Biotechnology, Guiyang, Guizhou, 550006, China.|Ecological Engineering College, Guizhou University of Engineering Science, Bijie, Guizhou, 551700, China.
Xiuxiu
X
Ren
Institute of Microbiology, State Key Laboratory of Mycology, Chinese Academy of Sciences, Beijing, 100101, China.
Xinyu
X
Zhang
Institute of Excellence in Fungal Research, Mae Fah Luang University, Chiang Rai, 57100, Thailand.
Kevin D
KD
Hyde
Big Genome Institute, Shenzhen, 518083, China.
Yongfeng
Y
Liu
Guizhou Key Laboratory of Agricultural Biotechnology, Guiyang, Guizhou, 550006, China. gzliuzuoyi@163.com.|Guizhou Academy of Agricultural Sciences, Guiyang, Guizhou, 550006, China. gzliuzuoyi@163.com.
Zuoyi
Z
Liu
D001230:Aspergillus / Q000145:classification / Q000235:genetics* / Q000378:metabolism / Q000648:ultrastructure; D005075:Biological Evolution; D019295:Computational Biology / Q000379:methods; D005285:Fermentation; D005656:Fungal Proteins / Q000235:genetics; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal; D016681:Genome, Fungal; D023281:Genomics / Q000379:methods; D059014:High-Throughput Nucleotide Sequencing; D020935:MAP Kinase Signaling System; D058977:Molecular Sequence Annotation; D005810:Multigene Family; D010802:Phylogeny; D040641:Quantitative Trait Loci; D013662:Tea / Q000378:metabolism / Q000382:microbiology*; D059467:Transcriptome
D005656:Fungal Proteins; D013662:Tea
Aspergillus cristatus; Genome; HOG pathway; Mating-typing gene loci; Mycotoxin