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Species-specific chitin-binding module 18 expansion in the amphibian pathogen Batrachochytrium dendrobatidis.

Abramyan J, Stajich JE - MBio (2012)

Bottom Line: Such shifts in lifestyle are generally accompanied by various degrees of genomic modifications, yet neither its mode of pathogenicity nor any factors associated with it have ever been identified.The expansion of CBM18 in B. dendrobatidis is exceptional in its size and diversity compared to other pathogenic species of fungi, making this genomic feature unique in an evolutionary context as well as in pathogenicity.Due to the alarming rate of worldwide spread and associated decline in amphibian populations, it is imperative to incorporate novel genomic and genetic techniques into the study of this species.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Pathology and Microbiology, University of California, Riverside, California, USA.

ABSTRACT

Unlabelled: Batrachochytrium dendrobatidis is the causative agent of chytridiomycosis, which is considered one of the driving forces behind the worldwide decline in populations of amphibians. As a member of the phylum Chytridiomycota, B. dendrobatidis has diverged significantly to emerge as the only pathogen of adult vertebrates. Such shifts in lifestyle are generally accompanied by various degrees of genomic modifications, yet neither its mode of pathogenicity nor any factors associated with it have ever been identified. Presented here is the identification and characterization of a unique expansion of the carbohydrate-binding module family 18 (CBM18), specific to B. dendrobatidis. CBM (chitin-binding module) expansions have been likened to the evolution of pathogenicity in a variety of fungus species, making this expanded group a prime candidate for the identification of potential pathogenicity factors. Furthermore, the CBM18 expansions are confined to three categories of genes, each having been previously implicated in host-pathogen interactions. These correlations highlight this specific domain expansion as a potential key player in the mode of pathogenicity in this unique fungus. The expansion of CBM18 in B. dendrobatidis is exceptional in its size and diversity compared to other pathogenic species of fungi, making this genomic feature unique in an evolutionary context as well as in pathogenicity.

Importance: Amphibian populations are declining worldwide at an unprecedented rate. Although various factors are thought to contribute to this phenomenon, chytridiomycosis has been identified as one of the leading causes. This deadly fungal disease is cause by Batrachochytrium dendrobatidis, a chytrid fungus species unique in its pathogenicity and, furthermore, its specificity to amphibians. Despite more than two decades of research, the biology of this fungus species and its deadly interaction with amphibians had been notoriously difficult to unravel. Due to the alarming rate of worldwide spread and associated decline in amphibian populations, it is imperative to incorporate novel genomic and genetic techniques into the study of this species. In this study, we present the first reported potential pathogenicity factors in B. dendrobatidis. In silico studies such as this allow us to identify putative targets for more specific molecular analyses, furthering our hope for the control of this pathogen.

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Related in: MedlinePlus

CBM18 domain phylogeny. Unrooted phylogram constructed using only domain sequences and implemented in BEAST v. 1.6.1 (65). H. polyrhiza domains were used as an outgroup and are represented in black. Domain names consist of the corresponding gene identifier, the phylogenetic group to which the domain belongs to, and the position in the gene which the specific domain holds. Thicker branches indicate Bayesian posterior probabilities of ≥0.80. ω values are given on branches which show positive selection. Branches are color coded according to gene type. TL, tyrosinase-like; DL, deacetylase-like; LL, lectin-like; HP, H. polyrhiza.
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fig2: CBM18 domain phylogeny. Unrooted phylogram constructed using only domain sequences and implemented in BEAST v. 1.6.1 (65). H. polyrhiza domains were used as an outgroup and are represented in black. Domain names consist of the corresponding gene identifier, the phylogenetic group to which the domain belongs to, and the position in the gene which the specific domain holds. Thicker branches indicate Bayesian posterior probabilities of ≥0.80. ω values are given on branches which show positive selection. Branches are color coded according to gene type. TL, tyrosinase-like; DL, deacetylase-like; LL, lectin-like; HP, H. polyrhiza.

Mentions: After the characterization of the CBM containing loci, the 67 individual domain sequences were isolated and aligned with the 10 from the outgroup H. polyrhiza (Fig. 2). This alignment was then used to build a phylogram using a Bayesian analysis in order to understand the relationship of the domains within and between loci. The Bayesian analysis revealed a relationship between domains that varies significantly from that of their parent loci. To simplify our analysis, we decided to partition the large number of domains further by assigning a letter to each monophyletic clade, referred to here as groups (Fig. 2).


Species-specific chitin-binding module 18 expansion in the amphibian pathogen Batrachochytrium dendrobatidis.

Abramyan J, Stajich JE - MBio (2012)

CBM18 domain phylogeny. Unrooted phylogram constructed using only domain sequences and implemented in BEAST v. 1.6.1 (65). H. polyrhiza domains were used as an outgroup and are represented in black. Domain names consist of the corresponding gene identifier, the phylogenetic group to which the domain belongs to, and the position in the gene which the specific domain holds. Thicker branches indicate Bayesian posterior probabilities of ≥0.80. ω values are given on branches which show positive selection. Branches are color coded according to gene type. TL, tyrosinase-like; DL, deacetylase-like; LL, lectin-like; HP, H. polyrhiza.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3569864&req=5

fig2: CBM18 domain phylogeny. Unrooted phylogram constructed using only domain sequences and implemented in BEAST v. 1.6.1 (65). H. polyrhiza domains were used as an outgroup and are represented in black. Domain names consist of the corresponding gene identifier, the phylogenetic group to which the domain belongs to, and the position in the gene which the specific domain holds. Thicker branches indicate Bayesian posterior probabilities of ≥0.80. ω values are given on branches which show positive selection. Branches are color coded according to gene type. TL, tyrosinase-like; DL, deacetylase-like; LL, lectin-like; HP, H. polyrhiza.
Mentions: After the characterization of the CBM containing loci, the 67 individual domain sequences were isolated and aligned with the 10 from the outgroup H. polyrhiza (Fig. 2). This alignment was then used to build a phylogram using a Bayesian analysis in order to understand the relationship of the domains within and between loci. The Bayesian analysis revealed a relationship between domains that varies significantly from that of their parent loci. To simplify our analysis, we decided to partition the large number of domains further by assigning a letter to each monophyletic clade, referred to here as groups (Fig. 2).

Bottom Line: Such shifts in lifestyle are generally accompanied by various degrees of genomic modifications, yet neither its mode of pathogenicity nor any factors associated with it have ever been identified.The expansion of CBM18 in B. dendrobatidis is exceptional in its size and diversity compared to other pathogenic species of fungi, making this genomic feature unique in an evolutionary context as well as in pathogenicity.Due to the alarming rate of worldwide spread and associated decline in amphibian populations, it is imperative to incorporate novel genomic and genetic techniques into the study of this species.

View Article: PubMed Central - PubMed

Affiliation: Department of Plant Pathology and Microbiology, University of California, Riverside, California, USA.

ABSTRACT

Unlabelled: Batrachochytrium dendrobatidis is the causative agent of chytridiomycosis, which is considered one of the driving forces behind the worldwide decline in populations of amphibians. As a member of the phylum Chytridiomycota, B. dendrobatidis has diverged significantly to emerge as the only pathogen of adult vertebrates. Such shifts in lifestyle are generally accompanied by various degrees of genomic modifications, yet neither its mode of pathogenicity nor any factors associated with it have ever been identified. Presented here is the identification and characterization of a unique expansion of the carbohydrate-binding module family 18 (CBM18), specific to B. dendrobatidis. CBM (chitin-binding module) expansions have been likened to the evolution of pathogenicity in a variety of fungus species, making this expanded group a prime candidate for the identification of potential pathogenicity factors. Furthermore, the CBM18 expansions are confined to three categories of genes, each having been previously implicated in host-pathogen interactions. These correlations highlight this specific domain expansion as a potential key player in the mode of pathogenicity in this unique fungus. The expansion of CBM18 in B. dendrobatidis is exceptional in its size and diversity compared to other pathogenic species of fungi, making this genomic feature unique in an evolutionary context as well as in pathogenicity.

Importance: Amphibian populations are declining worldwide at an unprecedented rate. Although various factors are thought to contribute to this phenomenon, chytridiomycosis has been identified as one of the leading causes. This deadly fungal disease is cause by Batrachochytrium dendrobatidis, a chytrid fungus species unique in its pathogenicity and, furthermore, its specificity to amphibians. Despite more than two decades of research, the biology of this fungus species and its deadly interaction with amphibians had been notoriously difficult to unravel. Due to the alarming rate of worldwide spread and associated decline in amphibian populations, it is imperative to incorporate novel genomic and genetic techniques into the study of this species. In this study, we present the first reported potential pathogenicity factors in B. dendrobatidis. In silico studies such as this allow us to identify putative targets for more specific molecular analyses, furthering our hope for the control of this pathogen.

Show MeSH
Related in: MedlinePlus