Draft genome and annotation of Aspergillus affinis (Circumdati): first insights into a biotech perspective

Aspergillus affinis (section Circumdati), a promising candidate for biomass bioconversion, produces ochratoxin A (OTA) that in possible contamination can be a threat to human health. However, little is known about its OTA biosynthetic genes. The whole-genome sequence of A. affinis may elucidate several aspects including its potential suitability in biomass bioconvesion at a pilot scale. Here, the nuclear and the mitochondrial (mt) genomes of A. affinis ATCC MYA-4773 T were sequenced, assembled and annotated. OTA-producing Aspergillus species of the section Circumdati (A. ochraceus fc-1, A. persii NRRL 35669, A. steynii IBT 23096, A. westerdijkiae CBS 112803) with available complete genome sequences on databases were used for comparison. The mt genome (31.7 Kb, GC % 25.3) contained core genes and accessory genes as well. Gene annotation for the nuclear genome (37 Mb, GC % 50.1) resulted in 11,386 genes, which were further classified according to GO terms and the CAZy databases. Among the 360 CAZymes identified, the GH family enzyme genes included cellulases (GH5, GH6), endo-1,4-ß-glucanases (GH5, GH7), xylanases (GH10), amylases (GH13_1, GH31), and inulinases (GH32), which may be of outstanding importance for white biotechnology. In general, the numbers of CAZy genes related to plant biomass degradation followed the phylogeny of Aspergillus section Circumdati. Among the SM biosynthetic gene clusters predicted, the OTA biosynthetic pathway cluster contained genes encoding a pks (AaOTApks), a nrps (AaOTAnrps), a cytochrome P450 monooxygenase (AaOTAp450), a halogenase (AaOTAhal), and a basic leucine zipper transcription factor (AaOTAbZip). In addition, genes encoding hypothetical proteins were present although the genetic synteny conservation found in relation to the Aspergillus species here examined. OTA gene cluster contains target genes suitable for developing new genetic tools for rapid and accurate control methods of ochratoxigenic Aspergillus strains.