Characterization of galectin-1 from Chinese giant salamanders Andrias davidianus and its involvements during immune response.

Galectins are considered as a multifunctional protein which play essential roles in cell adhesion and apoptosis, inflammation, tumor progression and immune response. In spite of extensive studies of galectin importance in immune system among different animals, few studies have been devoted to their functions in amphibian. In the present study, we characterized one proto type of galectin (named AdGal1) from Chinese giant salamander Andrias davidianus and studied its function in immune response. AdGal1 cDNA possesses an open reading frame of 598 bp, which encodes a putative galectin of 134 amino acids containing one carbohydrate recognition domains (CRDs). The constitutive expression of mRNA transcripts was detected in a wide range of tissues, with the highest expression in kidney. Immune challenges with Aeromonas hydrophila and Chinese giant salamander iridovirus (GSIV), the transcript level of AdGal1 in kidney was significantly upregulated. The mature protein of AdGal1 was successfully expressed and purified in Escherichia coli BL21 (DE3). The recombinant AdGal1 (rAdGal1) could show bind activity to different Gram negative and Gram positive bacteria. It could also strongly agglutinate different kinds of bacteria at different concentrations. Collectively, these data from the present study indicate that AdGal1 is a vital pattern recognition receptor to recognize different microbes in the innate immune system of Andrias davidianus.

RNA-Seq analysis and gene discovery of Andrias davidianus using Illumina short read sequencing.

The Chinese giant salamander, Andrias davidianus, is an important species in the course of evolution; however, there is insufficient genomic data in public databases for understanding its immunologic mechanisms. High-throughput transcriptome sequencing is necessary to generate an enormous number of transcript sequences from A. davidianus for gene discovery. In this study, we generated more than 40 million reads from samples of spleen and skin tissue using the Illumina paired-end sequencing technology. De novo assembly yielded 87,297 transcripts with a mean length of 734 base pairs (bp). Based on the sequence similarities, searching with known proteins, 38,916 genes were identified. Gene enrichment analysis determined that 981 transcripts were assigned to the immune system. Tissue-specific expression analysis indicated that 443 of transcripts were specifically expressed in the spleen and skin. Among these transcripts, 147 transcripts were found to be involved in immune responses and inflammatory reactions, such as fucolectin, ß-defensins and lymphotoxin beta. Eight tissue-specific genes were selected for validation using real time reverse transcription quantitative PCR (qRT-PCR). The results showed that these genes were significantly more expressed in spleen and skin than in other tissues, suggesting that these genes have vital roles in the immune response. This work provides a comprehensive genomic sequence resource for A. davidianus and lays the foundation for future research on the immunologic and disease resistance mechanisms of A. davidianus and other amphibians.