Comparative transcriptome analyses of seven anurans reveal functions and adaptations of amphibian skin

Abstract

Animal skin, which is the tissue that directly contacts the external surroundings, has evolved diverse functions to adapt to various environments. Amphibians represent the transitional taxon from aquatic to terrestrial life. Exploring the molecular basis of their skin function and adaptation is important to understand the survival and evolutionary mechanisms of vertebrates. However, comprehensive studies on the molecular mechanisms of skin functions in amphibians are scarce. In this study, we sequenced the skin transcriptomes of seven anurans belonging to three families and compared the similarities and differences in expressed genes and proteins. Unigenes and pathways related to basic biological processes and special functions, such as defense, immunity, and respiration, were enriched in functional annotations. A total of 108 antimicrobial peptides were identified. The highly expressed genes were similar in species of the same family but were different among families. Additionally, the positively selected orthologous groups were involved in biosynthesis, metabolism, immunity, and defense processes. This study is the first to generate extensive transcriptome data for the skin of seven anurans and provides unigenes and pathway candidates for further studies on amphibian skin function and adaptation.

Proteomic analysis of the skin from Chinese fire-bellied newt and comparison to Chinese giant salamander

“…According to the results of GO terms, basic biological and metabolic processes were largely enriched. Similar findings have been reported in frogs (Zhang et al, 2009;Huang et al, 2016). Additionally, amphibian skin has evolved complex structures and functions that allow amphibians to live in both water and land (Chuong et al, 2002).…”

“…It has been reported that amphibian skin secretions have anti-inflammatory, antibacterial, and antioxidant functions, and promote wound healing (Konig et al, 2015;Xu and Lai, 2015). Until now, the studies on the transcriptome (Huang et al, 2016), antioxidant peptidomes (Yang et al, 2009) and secretomes (Thompson et al, 2007) and proteomes (Wu et al, 2011) of frog skin have made great progress. In this study, we generated proteomics data of the newt skin using two-dimensional electrophoresis and MALDI-TOF/MS, and compared the protein kinds and expression values in the newt and giant salamander skin.…”

“…Presently, transcriptome (Huang et al, 2016), antioxidant peptidomics (Yang et al, 2009) and secretomics (Thompson et al, 2007) analysis of the skin in anuran amphibians have been reported. Meantime, the underlying molecular mechanisms of skin function and adaptation in anuran amphibians have been preliminarily explored.…”

Transcriptome analysis reveals the genetic basis underlying the seasonal development of keratinized nuptial spines in Leptobrachium boringii

“…All of these factors combined with the absence of genomic information for L. boringii would have caused the failure of functional annotation of a part of the identified unigenes. However, considering that previous studies successfully annotated approximately 25,000 genes in other non-model amphibian species, such as Odorrana margaretae , Megophrys sangzhiensis and Rhacophorus omeimontis [34, 37], our gene annotation results (more than 29,000 unigenes annotated) from L. boringii ’s transcriptome can be considered as high quality.…”

First de-novo transcriptome assembly of a South American frog, Oreobates cruralis, enables population genomic studies of Neotropical amphibians

“…The "general function" category (3,166; 24.37%) represented the largest group, 454 followed by "defense mechanisms" (1,421; 10.94%). Our results showed that genes related to defense 455 functions may be relatively abundant in the transcriptome of O. cruralis, particularly compared to the 456 seven anurans studied by Huang et al (2016) and also to A. mexicanum (Wu et al 2013 Although large genome size renders complete genome sequencing practically unfeasible in many 515 species, such as most amphibians, transcriptome sequencing represents a cost-effective alternative to 516 obtain a large amount of genome-wide data. This can allow advances in the study of ecological and 517 evolutionary processes beyond the limits imposed by the use of small panels of markers.…”