Transcriptome characterization and development of functional polymorphic SSR marker resource for Himalayan endangered species, Taxus contorta (Griff) Check

摘要

Taxus contorta is an important medicinal plant currently listed as endangered in IUCN Red Data List. It produces an anticancer drug, paclitaxel which is well known in the industrial sector. Due to habitat destruction and overexploitation, it is at the verge of extinction. Genomic and transcriptomic data for this species is scarce which has hampered its genomic studies. Moreover, large scale polymorphic informative codominant marker resource is also scarce which hinders its population and landscape genetic analysis. Here, we generated a reference transcriptome for this species which would facilitate the understanding of the functional elements and promote genomic research in this species. Also, a robust polymorphic SSR marker resource was characterized which can be used in conservation of this species. More than 100 million paired end raw reads were obtained through Illumina sequencing. A total of 129,869 unigenes with mean sequence length of 1244 nt were obtained from 209,860 de novo assembled transcripts. Of these, 35,752 transcripts were assigned 5971 unique GO terms. Around 40,386 transcripts were found to have 2163 unique Pfam Ids. Pathway analysis against KEGG database yielded 3721 unique enzyme numbers. Screening of the transcripts for microsatellite regions yielded 7041 SSRs. Among the 100 SSRs selected for characterization on 30 genotypes, 37 polymorphic markers showed a total of 214 alleles with mean of 5.78 alleles per locus. Mean effective number of alleles (Ne) was found to be 3.64 and average PIC value of 0.64 was observed. Observed heterozygosity (0.57) was found to be lower than expected (0.69). This effective polymorphic SSR marker resource will act as valuable tool for deciphering its genetic diversity.