Analysis of expressed sequence tags from Ginkgo mature foliage in China
Ginkgo biloba L. is a tree native to China, which has large importance within medicine and horticulture. The extracts from Ginkgo mature leaves with rich flavonoids and terpenoids are commonly used for a variety of folk remedies. We constructed a cDNA library derived from mature leaves of Ginkgo, which consisted of 8.12 × 105 clones with the insert length of 500–2,000 bp. We performed an analysis of expressed sequence tags (ESTs) and obtained partial sequences from 2,039 clones, which represented 1,437 unigenes consisting of 249 contigs and 1,188 singletons. The 2,039 ESTs were submitted to GenBank (dbEST) at NCBI and were assigned GenBank accession numbers from GE647881 to GE649919. The 1,235 cDNA clones out of 2,039 (60.1%) were assigned putative functions, and the remaining 804 clones were not similar to any known gene sequences in the databases. The five largest categories of Ginkgo clones were: “energy” (19.4%), “disease/defense” (16%), “metabolism” (11.3%), “unclassified proteins” (12.5%), and "secondary metabolism" (9%). The highly expressed transcripts in the cDNA library were some genes related to photosynthesis, disease/defense, and flavonoid biosynthesis, including ribulose–bisphosphate carboxylase small-chain gene, pathogenesis-related protein gene, light-harvesting chlorophyll a/b binding protein of photosystem gene, catalase gene, and phenylcoumaran benzylic ether reductase gene et al. Many genes with ESTs similar to photosynthesis, secondary metabolism, and stress-response genes were characterized. The analysis of ESTs indicates that it is a useful approach for isolating Ginkgo genes homologous to known genes. Our results provide new information about mature leaf-specific transcripts of Ginkgo.
KeywordsMature foliage cDNA library Expressed sequence tags Ginkgo
Contiguous consensus sequences
Cetyl trimethyl ammonium bromide
Expressed sequence tags
This study was supported by the Key Program of Educational Bureau of Hunan Province in China (No.04A064) and was granted by the Program of National Natural Science Foundation of China (No. 30471417).
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