Comprehensive Transcriptome Profiling and Functional Analysis of the Frog (Bombina maxima) Immune System

Abstract

Amphibians occupy a key phylogenetic position in vertebrates and evolution of the immune system. But, the resources of its transcriptome or genome are still little now. Bombina maxima possess strong ability to survival in very harsh environment with a more mature immune system. We obtained a comprehensive transcriptome by RNA-sequencing technology. 14.3% of transcripts were identified to be skin-specific genes, most of which were not isolated from skin secretion in previous works or novel non-coding RNAs. 27.9% of transcripts were mapped into 242 predicted KEGG pathways and 6.16% of transcripts related to human disease and cancer. Of 39 448 transcripts with the coding sequence, at least 1501 transcripts (570 genes) related to the immune system process. The molecules of immune signalling pathway were almost presented, several transcripts with high expression in skin and stomach. Experiments showed that lipopolysaccharide or bacteria challenge stimulated pro-inflammatory cytokine production and activation of pro-inflammatory caspase-1. These frog's data can remarkably expand the existing genome or transcriptome resources of amphibians, especially immunity data. The entity of the data provides a valuable platform for further investigation on more detailed immune response in B. maxima and a comparative study with other amphibians.

Host-derived, pore-forming toxin–like protein and trefoil factor complex protects the host against microbial infection

“…The other data are representative of at least two independent experiments. that most inflammasome-related elements are conserved in B. maxima, such as NLRP proteins, caspases, and IL-1β (8), suggesting that βγ-CAT also triggers IL-1β maturation and release in frogs via inflammasomes.…”

“…Our previous study demonstrated that B. maxima possesses an immune system similar to that of mammals (8). A 72-kDa complex of bacterial pore-forming toxin (PFT) aerolysin-like protein (α-subunit) and trefoil factor (TFF) (β-subunit) with a noncovalently linked form of αβ 2 was recently identified in the skin secretions of this species.…”

Aerolysin and Related Aeromonas Toxins

“…It has also appeared that aerolysin is the founding member of a large superfamily of proteins, members of which are present in all kingdoms. While some of these proteins are likely to be involved in attack mechanisms as aerolysin, others clearly must have different functions such as the aerolysinlike subunit of the betagamma-CAT of the Bombina maxima frog, which might be a component of its immune system [24] or Aerub (pXO2-60), a putative protein produced by Bacillus anthracis in which the aerolysin domain is fused to a ubiquitinlike domain [22]. Future studies on these proteins should reveal how the aerolysin fold, its oligomerization, and pore formation properties can be used for various purposes.…”

“…An interesting new addition is betagamma-CAT, a protein complex expressed by the frog species, Bombina maxima, which contains an aerolysinlike protein subunit and two trefoil factor subunits [23]. Betagamma-CAT might be a component of the B. maxima immune system, which is very similar to that of mammals [24] and would help the frog live in harsh environments, such as microorganism-rich mud pools.…”

AmphiBase: A new genomic resource for non‐model amphibian species

“…The resource, AmphiBase, is primarily based on transcriptome data. The large number of recent transcriptome studies in non‐model amphibian organisms (Abdullayev, Kirkham, Björklund, Simon, & Sandberg, ; Christenson et al, ; Gerchen et al, ; Qiao, Yang, Fu, & Song, ; Reilly, Schlipalius, Cramp, Ebert, & Franklin, ; Shao et al, ; Stewart et al, ; Yang et al, ; Zhao et al, ), together with four published amphibian genomes (Hellsten et al, ; Keinath et al, ; Session et al, ; Sun et al, ), represent sufficient available raw data to build an initial public version of AmphiBase. When additional transcriptome data from various amphibian species are accumulated in the near future, this resource will become more powerful for application in understanding of the evolution of amphibians and how they may serve as models for human disease.…”