Large scale in-silico identification and characterization of simple sequence repeats (SSRs) from de novo assembled transcriptome of Catharanthus roseus (L.) G. Don.

Transcriptomic data of C. roseus offering ample sequence resources for providing better insights into gene diversity: large resource of genic SSR markers to accelerate genomic studies and breeding in Catharanthus . Next-generation sequencing is an efficient system for generating high-throughput complete transcripts/genes and developing molecular markers. We present here the transcriptome sequencing of a 26-day-old Catharanthus roseus seedling tissue using Illumina GAIIX platform that resulted in a total of 3.37 Gb of nucleotide sequence data comprising 29,964,104 reads which were de novo assembled into 26,581 unigenes. Based on similarity searches 58 % of the unigenes were annotated of which 13,580 unique transcripts were assigned 5016 gene ontology terms. Further, 7,687 of the unigenes were found to have Cluster of Orthologous Group classifications, and 4,006 were assigned to 289 Kyoto Encyclopedia of Genes and Genome pathways. Also, 5,221 (19.64 %) of transcripts were distributed to 81 known transcription factor (TF) families. In-silico analysis of the transcriptome resulted in identification of 11,004 SSRs in 26.62 % transcripts from which 2,520 SSR markers were designed which exhibited a non-random pattern of distribution. The most abundant was the trinucleotide repeats (AAG/CTT) followed by the dinucleotide repeats (AG/CT). Location specific analysis of SSRs revealed that SSRs were preferentially associated with the 5'-UTRs with a predicted role in regulation of gene expression. A PCR validation of a set of 48 primers revealed 97.9 % successful amplification, and 76.6 % of them showed polymorphism across different Catharanthus species as well as accessions of C. roseus. In summary, this study will provide an insight into understanding the seedling development and resources for novel gene discovery and SSR development for utilization in marker-assisted selective breeding in C. roseus.