Glycoside hydrolases family 20 (GH20) represent putative virulence factors that are shared by animal pathogenic oomycetes, but are absent in phytopathogens.

BACKGROUND: Although interest in animal pathogenic oomycetes is increasing, the molecular basis mediating oomycete-animal relationships remains virtually unknown. Crinkler (CRN) genes, which have been traditionally associated with the cytotoxic activity displayed by plant pathogenic oomycetes, were recently detected in transcriptome sequences from the entomopathogenic oomycete Lagenidium giganteum, suggesting that these genes may represent virulence factors conserved in both animal and plant pathogenic oomycetes. In order to further characterize the L. giganteum pathogenome, an on-going genomic survey was mined to reveal novel putative virulence factors, including canonical oomycete effectors Crinkler 13 (CRN13) orthologs. These novel sequences provided a basis to initiate gene expression analyses and determine if the proposed L. giganteum virulence factors are differentially expressed in the presence of mosquito larvae (Aedes aegypti). RESULTS: Sequence analyses revealed that L. giganteum express CRN13 transcripts. The predicted proteins, like other L. giganteum CRNs, contained a conserved LYLA motif at the N terminal, but did not display signal peptides. In contrast, other potential virulence factors, such as Glycoside Hydrolases family 20 (hexosaminidase) and 37 (trehalase) proteins (GH20 and GH37), contained identifiable signal peptides. Genome mining demonstrated that GH20 genes are absent from phytopathogenic oomycete genomes, and that the L. giganteum GH20 sequence is the only reported peronosporalean GH20 gene. All other oomycete GH20 homologs were retrieved from animal pathogenic, saprolegnialean genomes. Furthermore, phylogenetic analyses demonstrated that saprolegnialean and peronosporalean GH20 protein sequences clustered in unrelated clades. The saprolegnialean GH20 sequences appeared as a strongly supported, monophyletic group nested within an arthropod-specific clade, suggesting that this gene was acquired via a lateral gene transfer event from an insect or crustacean genome. In contrast, the L. giganteum GH20 protein sequence appeared as a sister taxon to a plant-specific clade that included exochitinases with demonstrated insecticidal activities. Finally, gene expression analyses demonstrated that the L. giganteum GH20 gene expression level is significantly modulated in the presence of mosquito larvae. In agreement with the protein secretion predictions, CRN transcripts did not show any differential expression. CONCLUSIONS: These results identified GH20 enzymes, and not CRNs, as potential pathogenicity factors shared by all animal pathogenic oomycetes.

Description of three novel Lagenidium (Oomycota) species causing infection in mammals / Descripción de tres nuevas especies del género Lagenidium (Oomycota) responsables de infecciones en mamíferos

Background. Recent molecular phylogenetic analysis of Lagenidium strains recovered from subcutaneous lesions in cats, dogs, and a human with lagenidiosis resolved into four clades; one of them was Lagenidium giganteum, but three others were novel. Aims. Due to the recent increase in L. giganteum infections from mammals, we studied 21 Lagenidium strains isolated from dogs and a human available in our collection. Methods. Molecular phylogenetic studies and phenotypic characteristics were used to characterize the strains. Results. We report the finding of three novel species, herein designated as Lagenidium ajelloi, sp. nov., Lagenidium albertoi sp. nov, and Lagenidium vilelae sp. nov. Their morphological and growth features are also presented. Conclusions. Our study revealed the presence of three novel Lagenidium species infecting mammals (AU)

Antecedentes. Estudios recientes, basados en análisis filogenéticos, han revelado la existencia de cuatro clados de Lagenidium aislados en lesiones subcutáneas de gatos, perros y de un ser humano con lagenidiosis. Uno de los aislamientos se identificó como Lagenidium giganteum, pero los otros tres se consideraron especies nuevas. Objetivos. Debido al incremento de las infecciones por L. giganteum en mamíferos, se han estudiado 21 aislamientos de Lagenidium procedentes de animales con lagenidiosis. Métodos. Los aislamientos se clasificaron fenotípicamente, además de llevar a cabo estudios de filogenia con ellos. Resultados. Se proponen tres nuevas especies de Lagenidium: Lagenidium ajelloi, sp. nov., Lagenidium albertoi, sp. nov., y Lagenidium vilelae, sp. nov. Se tratan también sus características morfológicas. Conclusiones. Nuestro estudio reveló la existencia de tres especies nuevas de Lagenidium responsables de infecciones en mamíferos (AU)

Description of three novel Lagenidium (Oomycota) species causing infection in mammals.

BACKGROUND: Recent molecular phylogenetic analysis of Lagenidium strains recovered from subcutaneous lesions in cats, dogs, and a human with lagenidiosis resolved into four clades; one of them was Lagenidium giganteum, but three others were novel. AIMS: Due to the recent increase in L. giganteum infections from mammals, we studied 21 Lagenidium strains isolated from dogs and a human available in our collection. METHODS: Molecular phylogenetic studies and phenotypic characteristics were used to characterize the strains. RESULTS: We report the finding of three novel species, herein designated as Lagenidium ajelloi, sp. nov., Lagenidium albertoi sp. nov, and Lagenidium vilelae sp. nov. Their morphological and growth features are also presented. CONCLUSIONS: Our study revealed the presence of three novel Lagenidium species infecting mammals.

Transcriptome analysis of the entomopathogenic oomycete Lagenidium giganteum reveals putative virulence factors.

A combination of 454 pyrosequencing and Sanger sequencing was used to sample and characterize the transcriptome of the entomopathogenic oomycete Lagenidium giganteum. More than 50,000 high-throughput reads were annotated through homology searches. Several selected reads served as seeds for the amplification and sequencing of full-length transcripts. Phylogenetic analyses inferred from full-length cellulose synthase alignments revealed that L giganteum is nested within the peronosporalean galaxy and as such appears to have evolved from a phytopathogenic ancestor. In agreement with the phylogeny reconstructions, full-length L. giganteum oomycete effector orthologs, corresponding to the cellulose-binding elicitor lectin (CBEL), crinkler (CRN), and elicitin proteins, were characterized by domain organizations similar to those of pathogenicity factors of plant-pathogenic oomycetes. Importantly, the L. giganteum effectors provide a basis for detailing the roles of canonical CRN, CBEL, and elicitin proteins in the infectious process of an oomycete known principally as an animal pathogen. Finally, phylogenetic analyses and genome mining identified members of glycoside hydrolase family 5 subfamily 27 (GH5_27) as putative virulence factors active on the host insect cuticle, based in part on the fact that GH5_27 genes are shared by entomopathogenic oomycetes and fungi but are underrepresented in nonentomopathogenic genomes. The genomic resources gathered from the L. giganteum transcriptome analysis strongly suggest that filamentous entomopathogens (oomycetes and fungi) exhibit convergent evolution: they have evolved independently from plant-associated microbes, have retained genes indicative of plant associations, and may share similar cores of virulence factors, such as GH5_27 enzymes, that are absent from the genomes of their plant-pathogenic relatives.