the chinese giant salamander ( a. davidianus ) belonging to one of the most primitive orders caudata , family cryptobranchidae , is the largest extant amphibian species in the world and found only in china , .
it was called  babyfish  mainly lives in chinese interior water area . being crown as a living fossil from 350  million  years ago , so it is considered to be a valuable model in edible value , medical value , view value , science value and so on .
the chinese giant salamander is classified as critically endangered by the international union for conservation of nature and natural resources ( iucn ) red list of threatened species , is a class ii on the national list of protected animals in china .
nonetheless , only a limited number of transcriptomes from a. davidianus have been sequenced so far , , , , . meanwhile , the genetic information and gene sequences about the chinese giant salamander in public databases are also scanty .
here we performed de novo transcriptome assembly for a. davidianus by next - generation sequencing .
the obtained transcriptomic data will be useful for further studies of the genomes evolution of a. davidianus may have represented transition steps from aquatic to terrestrial life .
the healthy a. davidianus were obtained from a farm located in luan chuan ( henan province , china ) .
organ tissues including spleen , liver , muscle , kidney , skin , testis , gut and heart collected from three - year - old ( 3y ) male a. davidianus immediately after dissection , washed in sterile pbs .
animals tissues sample for rna extraction were snap - frozen in liquid nitrogen and stored at   80  c for further analysis .
all experiments were performed in strict accordance with the animal protection law of china , and were approved by the review committee for the use of animal subjects of henan university of science and technology .
the a. davidianus were pooled from 8 tissues ( spleen , liver , muscle , kidney , skin , testis , gut and heart ) and used for total rnas library construction .
rna - seq libraries were generated using the truseq rna - seq sample prep kit according to the manufacturer 's protocol ( illumina inc . , san diego , ca ) .
first and second strand cdna synthesis were followed by end - repair and adenosines were added to the 3ends .
adapters were ligated to the cdna and 200    25  bp fragments were gel purified and enriched by pcr .
the libraries were quantified using bioanalyzer 2100 ( agilent technologies , santa clara , ca ) and run on the illumina hiseq2500 platform ( illumina inc . ) .
a total of 15,398,997,600  bp were obtained from sequencing libraries . after cleaning and quality checks , the de novo assembly of all sequencing data using the trinity program .
it generated 158,103 all - transcripts with an average length of 810  bp and an n50 of 1659  bp ; and 132,912 all unigenes were achieved with an average length of 690  bp and an n50 of 1263  bp ( table 1 ) .
of these , 34,075 were >  1  kb and 21,855 >  1  kb , respectively .
we annotated the all 71,443 unigenes to nr , nt , cdd , swissprot , trembl , pfam , kegg , kog and go databases .
a microsatellite program misa was also used to identify and localize microsatellite motifs.table 1summary of a. davidianus assembly statistics.table 1indexa .
davidianus unigenesall number158,103132,912length    500  bp59,71542,327length    1000  bp34,07521,855n50 length1659  bp1263  bpn90 length285  bp262  bpmax length16,067  bp16,067  bpminor length201  bp201  bpall length128,175,999  bp91,713,308  bpmean length810  bp690  bp summary of a. davidianus assembly statistics .
the healthy a. davidianus were obtained from a farm located in luan chuan ( henan province , china ) .
organ tissues including spleen , liver , muscle , kidney , skin , testis , gut and heart collected from three - year - old ( 3y ) male a. davidianus immediately after dissection , washed in sterile pbs .
animals tissues sample for rna extraction were snap - frozen in liquid nitrogen and stored at   80  c for further analysis .
all experiments were performed in strict accordance with the animal protection law of china , and were approved by the review committee for the use of animal subjects of henan university of science and technology .
the a. davidianus were pooled from 8 tissues ( spleen , liver , muscle , kidney , skin , testis , gut and heart ) and used for total rnas library construction .
rna - seq libraries were generated using the truseq rna - seq sample prep kit according to the manufacturer 's protocol ( illumina inc .
first and second strand cdna synthesis were followed by end - repair and adenosines were added to the 3ends .
adapters were ligated to the cdna and 200    25  bp fragments were gel purified and enriched by pcr .
the libraries were quantified using bioanalyzer 2100 ( agilent technologies , santa clara , ca ) and run on the illumina hiseq2500 platform ( illumina inc . ) .
a total of 15,398,997,600  bp were obtained from sequencing libraries . after cleaning and quality checks , the de novo assembly of all sequencing data using the trinity program .
it generated 158,103 all - transcripts with an average length of 810  bp and an n50 of 1659  bp ; and 132,912 all unigenes were achieved with an average length of 690  bp and an n50 of 1263  bp ( table 1 ) . of these , 34,075 were >  1  kb and 21,855 >  1  kb , respectively .
we annotated the all 71,443 unigenes to nr , nt , cdd , swissprot , trembl , pfam , kegg , kog and go databases .
a microsatellite program misa was also used to identify and localize microsatellite motifs.table 1summary of a. davidianus assembly statistics.table 1indexa .
davidianus unigenesall number158,103132,912length    500  bp59,71542,327length    1000  bp34,07521,855n50 length1659  bp1263  bpn90 length285  bp262  bpmax length16,067  bp16,067  bpminor length201  bp201  bpall length128,175,999  bp91,713,308  bpmean length810  bp690  bp summary of a. davidianus assembly statistics .
 next - generation technologies for determination of genomics and transcriptomics composition have a wide range of applications . 
 andrias davidianus , has become an endangered amphibian species of salamander endemic in china . 
 however , there is a lack of the molecular information . in this study 
 , we obtained the rna - seq data from a pool of a. davidianus tissue including spleen , liver , muscle , kidney , skin , testis , gut and heart using illumina hiseq 2500 platform . 
 a total of 15,398,997,600  bp were obtained , corresponding to 102,659,984 raw reads . 
 a total of 102,659,984 reads were filtered after removing low - quality reads and trimming the adapter sequences . 
 the trinity program was used to de novo assemble 132,912 unigenes with an average length of 690  bp and n50 of 1263  bp . 
 unigenes were annotated through number of databases . 
 these transcriptomic data of a. davidianus should open the door to molecular evolution studies based on the entire transcriptome or targeted genes of interest to sequence . the raw data in this study can be available in ncbi sra database with accession number of srp099564 . 
Direct link to deposited data
Introduction
Experimental design, materials and methods
Animal materials
Library construction and sequencing
De novo transcriptome assembly and functional annotation
Conflict of interest