西藏胡黄连根状茎差异表达基因的筛选及分析

 西藏胡黄连是著名的濒危西藏药材, 其粗壮的根茎部是重要的合成和储存药用萜类物质器官，萜类含量显著高于叶部。为克隆西藏胡黄连根状茎和叶的差异表达基因，利用抑制消减杂交技术，构建了根状茎特定的抑制消减文库。从该SSH文库中随机挑取片段不一的阳性克隆测序，采用Blastx进行同源比对，获得了27个表达序列标签（EST），并获登录号。序列统计分析结果表明，其中有11个EST在GenBank中无同源性序列，推测可能是新基因片断。蛋白质功能分类结果表明，这些蛋白质与翻译、能量代谢、转运与结合、细胞膜合成、氨基酸生物合成及中间代谢6大类蛋白功能有关。为深入研究与萜类生物合成直接或间接相关基因，选择了长595 bp的差异表达EST序列EX172715进行了同源比对和蛋白系统进化分析。结果表明，EX172715具有细胞色素P450单加氧酶的特征结构，与拟南芥的细胞色素P450单加氧酶蛋白的同源性高于水稻和小麦。提供了一组与西藏胡黄连次生代谢相关的新基因库。

The Screening and Analysis of Differentially Expressed Genes from Rhizome of Picrorhiza Scrophulariiflora

Picrorhiza scrophulariiflora is a rare and endangered Tibetan medicinal plant. Its rhizome is a specific biosynthesis and accumulation tissue for invaluable hepatoprotective iridoids. We applied SSH technique for elucidating the differential gene expression in rhizome and leaf of the plant and constructed a subtracted rhizomE-specific cDNA library. From the library, 27 non-redundant "EST-unigenes" were obtained and submitted to dbEST. Sequence analysis showed that 11 ESTs among the 27 ESTs are deducted to be novel genes (ESTs) with no significant homology to any known sequences within GenBank database and could potentially be regarded as novel gene fragments. These 27 ESTs are mainly associated with translation, energy metabolism, transport and binding, cell envelope, amino acid biosynthesis, and central intermediary metabolism. Finally, phylogenetic analyses implicated that a cytochrome monooxygenase P450-related gene (EX172715, 595 bp) identified from P. scrophulariiflora are more related to that from A. thaliana than that from O.sativa and T.aestivum. This study provides a novel gene pool involved in P.scrophulariiflora secondary metabolism.