pecies in the genus Aspergillus are of broad interest to medical 1 , applied 2,3 , and basic research 4. Members of Aspergillus section Nigri ('black aspergilli') are prolific producers of native and heterologous proteins 5,6 , organic acids (in particular citric acid 2,7,8), and secondary metabolites (including biopharmaceuticals and mycotoxins like ochratoxin A). Furthermore, the section members are generally very efficient producers of extracellular enzymes 9,10 ; they are the production organisms for 49 out of 260 industrial enzymes 11,12. Among the most important of these, in addition to A. niger, are A. tubingensis, A. aculeatus, and A. luchuensis (previously A. acidus, A. kawachii, and A. awamori 13-15 , respectively). Members of Aspergillus section Nigri are also known as destructive degraders of foods and feeds, and some isolates produce the potent mycotoxins ochratoxin A 16 and fumonisins 17-19. In addition, some species in this section have been proposed to be pathogenic to humans and other animals 20. It is thus of interest to further examine section Nigri for industrial exploitation, as well as prevention of food spoilage, toxin production, and pathogenicity caused by these fungi. A combined phylogenetic and phenotypic approach has shown that section Nigri contains at least 27 species 21-25. Recent results have shown that the section contains species with high diversity and may consist of two separate clades: the biseriate species and the uniseriate species 26 , which show differences in sexual states 27 , sclerotium formation 28 , and secondary metabolite production 29. In the section, only six species have had their genome sequenced: A. niger 2,8 , A. luchuensis 15,30 , A. carbonarius 31 , A. aculeatus 31 , A. tubingensis 31 , and A. brasiliensis 31. This section, with its combination of species richness and fungal species with a diverse impact on humanity, is thus particularly interesting for studying the diversification of fungi into species. In this study, we have de novo-sequenced the genomes of 20 species of section Nigri, thus completing a genome compendium of 26 described species in the section. Further, we have genome-sequenced three
The fungal kingdom is too large to be discovered exclusively by classical genetics. The access to omics data opens a new opportunity to study the diversity within the fungal kingdom and how adaptation to new environments shapes fungal metabolism. Genomes are the foundation of modern science but their quality is crucial when analysing omics data. In this study, we demonstrate how one gold-standard genome can improve functional prediction across closely related species to be able to identify key enzymes, reactions and pathways with the focus on primary carbon metabolism.Based on this approach we identified alternative genes encoding various steps of the different sugar catabolic pathways, and as such provided leads for functional studies into this topic. We also revealed significant diversity with respect to genome content, although this did not always correlate to the ability of the species to use the corresponding sugar as a carbon source.
BackgroundThe retinoblastoma tumour suppressor, Rb, has two major functions. First, it represses genes whose products are required for S-phase entry and progression thus stabilizing cells in G1. Second, Rb interacts with factors that induce cell-cycle exit and terminal differentiation. Dictyostelium lacks a G1 phase in its cell cycle but it has a retinoblastoma orthologue, rblA. Methodology/Principal FindingsUsing microarray analysis and mRNA-Seq transcriptional profiling, we show that RblA strongly represses genes whose products are involved in S phase and mitosis. Both S-phase and mitotic genes are upregulated at a single point in late G2 and again in mid-development, near the time when cell cycling is reactivated. RblA also activates a set of genes unique to slime moulds that function in terminal differentiation.ConclusionsLike its mammalian counterpart Dictyostelium, RblA plays a dual role, regulating cell-cycle progression and transcriptional events leading to terminal differentiation. In the absence of a G1 phase, however, RblA functions in late G2 controlling the expression of both S-phase and mitotic genes.
No genome sequencing project is complete without structural and functional annotation. Gene models and functional predictions for these models can be obtained relatively easily using computational methods, but they are prone to errors. We describe herein the steps we use to manually curate gene models and functionally annotate them. Our approach is to examine each gene model carefully, and improve its structure if necessary, using a comprehensive set of experimental and computational data as evidence. Then, functional predictions are assigned to the gene models based on conserved protein domains and sequence similarities. We use stringent sequence similarity cutoffs and reviewed sequence-database records as external sources for our annotations. By methodically choosing which evidence to use for each annotation, we minimize the risk of adopting and assigning false predictions to the gene models.
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