Hybrid Genome Assemblies of Marine Bacteria Isolated from the Sponge Sycon capricorn.

Sponges have complex relationships with bacteria, the roles of which include food, important components of the holobiont, pathogens, and accidentally accumulated elements of the environment. Consequently, sponges are reservoirs of microbial genomes and novel compounds. Therefore, we isolated and sequenced the whole genomes of bacterial species from the calcareous sponge Sycon capricorn.

Complete Genome Sequence of an Australian Strain of the Lichen-Forming Fungus Endocarpon pusillum (Hedwig).

The cosmopolitan lichen-forming fungus Endocarpon pusillum (Hedwig) has previously been used as a model for the study of symbiosis and drought resistance. Here, we present the annotated genome of the Australian strain Endocarpon pusillum EPUS1.4. This genome sequence provides additional information on the ability of this species to produce secondary metabolites.

Acquisition and Loss of Secondary Metabolites Shaped the Evolutionary Path of Three Emerging Phytopathogens of Wheat.

White grain disorder is a recently emerged wheat disease in Australia, caused by Eutiarosporella darliae, E. pseudodarliae, and E. tritici-australis. The disease cycle of these pathogens and the molecular basis of their interaction with wheat are poorly understood. To address this knowledge gap, we undertook a comparative genomics analysis focused on the secondary metabolite gene repertoire among these three species. This analysis revealed a diverse array of secondary metabolite gene clusters in these pathogens, including modular polyketide synthase genes. These genes have only been previously associated with bacteria and this is the first report of such genes in fungi. Subsequent phylogenetic analyses provided strong evidence that the modular PKS genes were horizontally acquired from a bacterial or a protist species. We also uncovered a secondary metabolite gene cluster with three polyketide/nonribosomal peptide synthase genes (Hybrid-1, -2, and -3) in E. darliae and E. pseudodarliae. In contrast, only remnant and partial genes homologous to this cluster were identified in E. tritici-australis, suggesting loss of this cluster. Homologues of Hybrid-2 in other fungi have been proposed to facilitate disease in woody plants, suggesting a possible alternative host range for E. darliae and E. pseudodarliae. Subsequent assays confirmed that E. darliae and E. pseudodarliae were both pathogenic on woody plants, but E. tritici-australis was not, implicating woody plants as potential host reservoirs for the fungi. Combined, these data have advanced our understanding of the lifestyle and potential host-range of these recently emerged wheat pathogens and shed new light on fungal secondary metabolism.

SnPKS19 Encodes the Polyketide Synthase for Alternariol Mycotoxin Biosynthesis in the Wheat Pathogen Parastagonospora nodorum.

Alternariol (AOH) is an important mycotoxin from the Alternaria fungi. AOH was detected for the first time in the wheat pathogen Parastagonospora nodorum in a recent study. Here, we exploited reverse genetics to demonstrate that SNOG_15829 (SnPKS19), a close homolog of Penicillium aethiopicum norlichexanthone (NLX) synthase gene gsfA, is required for AOH production. We further validate that SnPKS19 is solely responsible for AOH production by heterologous expression in Aspergillus nidulans. The expression profile of SnPKS19 based on previous P. nodorum microarray data correlated with the presence of AOH in vitro and its absence in planta. Subsequent characterization of the ΔSnPKS19 mutants showed that SnPKS19 and AOH are not involved in virulence and oxidative stress tolerance. Identification and characterization of the P. nodorum SnPKS19 cast light on a possible alternative AOH synthase gene in Alternaria alternata and allowed us to survey the distribution of AOH synthase genes in other fungal genomes. We further demonstrate that phylogenetic analysis could be used to differentiate between AOH synthases and the closely related NLX synthases. This study provides the basis for studying the genetic regulation of AOH production and for development of molecular diagnostic methods for detecting AOH-producing fungi in the future.