Construction of a full-length enriched cDNA library and analysis of 3111 ESTs from roots of Bupleurum chinense DC.

Radix Bupleuri (Chaihu), sourced from the dried roots of Bupleurum species, is a traditional Chinese medicine with anti-inflammatory, anti-pyretic, and anti-hepatotoxic efficacy. It is widely used ill China, Japan, Korea, and other Countries in south Asia. A full-length enriched cDNA library derived from the roots of B. chinense DC. was constructed for the first time by the SMART technique in this study to initiate the functional genomic research of this important medicinal plant. The titre of the library was 1.1 x 10(6). From the library, randomly selected 3902 clones were 5' single-pass sequenced, among which 3111 high quality ESTs were generated and 1650 uniESTs were identified with 377 contigs and 1273 singleton ESTs. The estimated average cDNA insert size was 1.1 kb, and the fullness ratio was ca. 51.5%. BlastX analysis of all uniESTs resulted in 949 (57.5%) homology to previously identified genes, 680 (41.2%) matched to unknown, unnamed, or hypothetical protein genes, and 21 clones had no hit. Gene ontology (GO) annotation Of uniESTs showed that approximately 1002, 957, and 861 were assigned molecular function, biological process, and cellular component GO terms, respectively. KEGG pathway analysis indicated that 307 uniESTs may be involved in 31 metabolic pathways, in which at least five uniESTs were contained, by comparing, each with Arabidopsis metabolic pathways. Through SSR searching within 1650 uniESTs. 86 potentially useful SSR loci were identified in 82 uniESTs. The library and EST data provide a platform to study the molecular mechanisms of various physiological phenomena of Bupleurum. The set of SSR loci would potentially be useful molecular markers for the germplasm identification, genetic diversity analysis, and gene mapping, of Bupleurum.