large-webbed bell toad (Bombina maxima) ( Image by Yang Jin)
The large-webbed bell toad (Bombina maxima), also names Chinese red belly frog is a species of toad in the Bombinatoridae family, which is endemic to Sichuan, Yunnan and Guizhou in China. It is characterized not only with his bright aposematic coloration on ventral region, but more importantly with his impressive capability to survive in very harsh environments, such as swamps, freshwater marshes, intermittent freshwater marshes, freshwater springs, arable land, and even canals and ditches.
The skin of frog is multi-tasks player. Its function includes breathing, moisture retaining, and thermo adjusting, as well as microbe menace defending based on the chemical punch packed in its skin secretions. According to currently available data, the adaptive immune system was suddenly emerged on vertebrate with jaws like a ‘big-bang’ event, so amphibians occupy a key phylogenetic position in vertebrates and evolution of the immune system.
“Although Xenopus is the most widely used model amphibians and some of its genome or transcriptome has been available, but from the living environment and skin secretions enriched with antimicrobial peptides, B. maxima could have a more mature immune system compared with Xenopus”, according to Prof. ZHANG Yun (Kunming Institute of Zoology). In his most recent research, the latest paired-end RNA-sequencing (RNA-seq) techniques have been adopted to identify the nature of innate or adaptive immunity in vertebrates.
In this study, by analyzing cDNAs extracted from skin and blood tissues, a comprehensive transcriptome of B. maxima has been obtained and the transcriptome differences between Xenopus and B. maxima have been showed. In particular, the active innate immune system and the nearly parallel adaptive immune system of B. maxima to mammals have been revealed. The data indicated that B. maxima has enriched gene transcripts (570 genes) related to diseases and disease pathways, especially to immunity. Meanwhile, abundant transcripts have identified to be skin-specific genes. Furthermore, the results showed the presence of inflammasome in B. maxima and its role in the defending infection.
ZHANG’s study remarkably expanded 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.
The database of the transcriptome will be submitted to public databases for free access very soon. Details could be obtained through http://dnaresearch.oxfordjournals.org/cgi/content/full/dst035? .
(By Su-Qing Liu)
