De novo assembly, transcriptome characterization and marker discovery in Indian major carp, Labeo rohita through pyrosequencing

Labeo rohita, one of the Indian major carps, is the most popular culture species in Indian subcontinent due to its consumer preference and delicacy. A selective breeding program for harvest body weight has resulted in an average genetic gain of 17% per generation. Transcriptome resource for this species is scanty. Here, we have characterized the liver and muscle transcriptomes of rohu using Roche 454 GS-FLX next generation sequencing platform. In total, 1.2 million reads were generated, de novo assembly and clustering resulted in 4171 transcripts. Out of these, 4171 had significant blast hit against NCBI nr database, and 2130 transcripts were successfully annotated. In total, 289 SSRs were identified with an identification rate of 5.8%, and dinucleotide repeat motifs were observed to be the most abundant SSRs. Further, 2231 putative SNPs were identified with high confidence. Validation of eight putative SNPs using Sanger sequencing resulted in 100% true SNPs. Significant allelic imbalance of M1, M4 and M5 loci between growth selected and control individual were observed. Furthermore, 13 transcription factors were identified in the present study belonging to six different transcription factor families. The present study demonstrated the utility of RNAseq to develop genomics resources in non-model fish species, and the marker resources developed would support the genetic improvement program of this species.

Automated summary

By analyzing the transcriptomes of Labeo rohita, a variety of genetic information related to genetic improvement, including SSRs and SNPs, were identified and the reliability of these genetic markers was verified. In addition, transcription factors that may influence genetic improvement of Labeo rohita were also discovered in this study.