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Phylogenetic and biogeographic implications inferred by mitochondrial intergenic region analyses and ITS1-5.8S-ITS2 of the entomopathogenic fungi Beauveria bassiana and B. brongniartii.

ABSTRACT: BACKGROUND: The entomopathogenic fungi of the genus Beauveria are cosmopolitan with a variety of different insect hosts. The two most important species, B. bassiana and B. brongniartii, have already been used as biological control agents of pests in agriculture and as models for the study of insect host - pathogen interactions. Mitochondrial (mt) genomes, due to their properties to evolve faster than the nuclear DNA, to contain introns and mobile elements and to exhibit extended polymorphisms, are ideal tools to examine genetic diversity within fungal populations and genetically identify a species or a particular isolate. Moreover, mt intergenic region can provide valuable phylogenetic information to study the biogeography of the fungus. RESULTS: The complete mt genomes of B. bassiana (32,263 bp) and B. brongniartii (33,920 bp) were fully analysed. Apart from a typical gene content and organization, the Beauveria mt genomes contained several introns and had longer intergenic regions when compared with their close relatives. The phylogenetic diversity of a population of 84 Beauveria strains -mainly B. bassiana (n = 76) - isolated from temperate, sub-tropical and tropical habitats was examined by analyzing the nucleotide sequences of two mt intergenic regions (atp6-rns and nad3-atp9) and the nuclear ITS1-5.8S-ITS2 domain. Mt sequences allowed better differentiation of strains than the ITS region. Based on mt and the concatenated dataset of all genes, the B. bassiana strains were placed into two main clades: (a) the B. bassiana s. l. and (b) the "pseudobassiana". The combination of molecular phylogeny with criteria of geographic and climatic origin showed for the first time in entomopathogenic fungi, that the B. bassiana s. l. can be subdivided into seven clusters with common climate characteristics. CONCLUSIONS: This study indicates that mt genomes and in particular intergenic regions provide molecular phylogeny tools that combined with criteria of geographic and climatic origin can subdivide the B. bassiana s.l. entomopathogenic fungi into seven clusters with common climate characteristics.

SUBMITTER: Ghikas DV

PROVIDER: S-EPMC2896372 | biostudies-literature | 2010

REPOSITORIES: biostudies-literature

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Phylogenetic and biogeographic implications inferred by mitochondrial intergenic region analyses and ITS1-5.8S-ITS2 of the entomopathogenic fungi Beauveria bassiana and B. brongniartii.

Ghikas Dimitri V DV Kouvelis Vassili N VN Typas Milton A MA

BMC microbiology 20100616

<h4>Background</h4>The entomopathogenic fungi of the genus Beauveria are cosmopolitan with a variety of different insect hosts. The two most important species, B. bassiana and B. brongniartii, have already been used as biological control agents of pests in agriculture and as models for the study of insect host - pathogen interactions. Mitochondrial (mt) genomes, due to their properties to evolve faster than the nuclear DNA, to contain introns and mobile elements and to exhibit extended polymorph ...[more]

PMID: 20553589

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Project description:Mosquito immunity studies have focused mainly on characterizing immune effector mechanisms elicited against parasites, bacteria and more recently, viruses. However, those elicited against entomopathogenic fungi remain poorly understood, despite the ubiquitous nature of these microorganisms and their unique invasion route that bypasses the midgut epithelium, an important immune tissue and physical barrier. Here, we used the malaria vector Anopheles gambiae as a model to investigate the role of melanization, a potent immune effector mechanism of arthropods, in mosquito defense against the entomopathogenic fungus Beauveria bassiana, using in vivo functional genetic analysis and confocal microscopy. The temporal monitoring of fungal growth in mosquitoes injected with B. bassiana conidia showed that melanin eventually formed on all stages, including conidia, germ tubes and hyphae, except the single cell hyphal bodies. Nevertheless, melanin rarely aborted the growth of any of these stages and the mycelium continued growing despite being melanized. Silencing TEP1 and CLIPA8, key positive regulators of Plasmodium and bacterial melanization in A. gambiae, abolished completely melanin formation on hyphae but not on germinating conidia or germ tubes. The detection of a layer of hemocytes surrounding germinating conidia but not hyphae suggested that melanization of early fungal stages is cell-mediated while that of late stages is a humoral response dependent on TEP1 and CLIPA8. Microscopic analysis revealed specific association of TEP1 with surfaces of hyphae and the requirement of both, TEP1 and CLIPA8, for recruiting phenoloxidase to these surfaces. Finally, fungal proliferation was more rapid in TEP1 and CLIPA8 knockdown mosquitoes which exhibited increased sensitivity to natural B. bassiana infections than controls. In sum, the mosquito melanization response retards significantly B. bassiana growth and dissemination, a finding that may be exploited to design transgenic fungi with more potent bio-control activities against mosquitoes.

Dataset Information

Phylogenetic and biogeographic implications inferred by mitochondrial intergenic region analyses and ITS1-5.8S-ITS2 of the entomopathogenic fungi Beauveria bassiana and B. brongniartii.

Publications

Phylogenetic and biogeographic implications inferred by mitochondrial intergenic region analyses and ITS1-5.8S-ITS2 of the entomopathogenic fungi Beauveria bassiana and B. brongniartii.

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