Institute of Medicinal Plant Development, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing 100193, PR China.
Physiol Plant. 2010 Feb;138(2):134-49. doi: 10.1111/j.1399-3054.2009.01309.x. Epub 2009 Oct 19.
American ginseng (Panax quinquefolius L.) has been used for a wide range of therapeutic purposes in China. The major bioactive phytochemicals responsible for this plant's pharmacological features are ginsenosides. Thus far, little is known regarding the genes involved in ginsenosides biosynthesis in this species. As a non-model plant, information about its genomes is generally not available. In this study, we generated 6678 expressed sequence tags (ESTs) from the flower, leaf and root cDNA libraries of American ginseng. Assembly of ESTs resulted in 3349 unigenes including 534 contigs (with ESTs number ranging from 2 to 52) and 2815 singletons. By analyzing the predominant transcripts within specific tissues, a gene expression pattern was obtained in a tissue-specific manner. They were assigned according to the functional classification of unigenes to broad ranges of Gene Ontology categories which include biological processes, cellular components and molecular functions. Based on blastx search results, 24 unigenes representing candidates related to ginsenosides biosynthesis were identified. Cloning and characterization of 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGR, EC: 1.1.1.34), the rate-limiting enzyme in mevalonic acid pathway, demonstrated that it belonged to the plant HMGR family and was highly expressed in leaves. Putative transcription factors were detected in 63 unigenes, including zinc finger, WRKY, homeobox and MADS-box family proteins. Five hundred and eighty-eight simple sequence repeat motifs were identified, of which, dimer was the most abundant motif. These data will provide useful information on transcript profiles, gene discovery, transcriptional regulation, flower biogenesis and marker-assisted selections. The analysis and information from this study will greatly contribute to the improvement of this medicinal plant as well as of other species in the Araliaceae family, for the purpose of ensuring adequate drug resources.
西洋参（Panax quinquefolius L.）在中国被广泛用于治疗各种疾病。负责这种植物药理学特征的主要生物活性植物化学物质是人参皂苷。到目前为止，对于这种植物中参与人参皂苷生物合成的基因知之甚少。作为一种非模式植物，其基因组信息通常不可用。在这项研究中，我们从西洋参的花、叶和根 cDNA 文库中生成了 6678 条表达序列标签（EST）。EST 组装产生了 3349 个单基因，包括 534 个串联体（EST 数量从 2 到 52）和 2815 个单基因。通过分析特定组织中主要转录物，以组织特异性方式获得基因表达模式。它们根据单基因的功能分类分配到广泛的基因本体论类别，包括生物过程、细胞成分和分子功能。根据blastx 搜索结果，鉴定了 24 个代表与人参皂苷生物合成相关的候选基因。克隆和表征 3-羟基-3-甲基戊二酰辅酶 A 还原酶（HMGR，EC：1.1.1.34），甲羟戊酸途径的限速酶，表明它属于植物 HMGR 家族，在叶片中高度表达。在 63 个单基因中检测到假定的转录因子，包括锌指、WRKY、同源盒和 MADS 盒家族蛋白。鉴定了 588 个简单序列重复基序，其中二聚体是最丰富的基序。这些数据将为转录谱、基因发现、转录调控、花发生和标记辅助选择提供有用的信息。该研究的分析和信息将极大地促进这种药用植物以及伞形科其他物种的改良，以确保有足够的药物资源。
