College of Life Science, Northeast Forestry University, Harbin 150040, China.
Mol Biol Rep. 2012 Mar;39(3):2321-8. doi: 10.1007/s11033-011-0982-0. Epub 2011 Jun 7.
Betulin and oleanolic acids (pentacyclic triterpenoid secondary metabolites) have broad pharmacological activities and can be potentially used for the development of anti-cancer and anti-AIDS drugs. In this study, we detected the accumulation and the distribution characteristics of betulin and oleanolic acid in various organs of white birch at different ages. We also determined the expression of 4 OSC genes (LUS, β-AS, CAS1 and CAS2) involved in the triterpenoid synthesis pathways by real time RT-PCR. The result showed that the 1-year old birch can synthesize betulin and oleanolic acid. In addition, betulin and oleanolic acids were mainly distributed in the bark, while the content in the root skin and leaf was very low. The content of betulin and oleanolic acid in birch varied in different seasons. The content of betulin and oleanolic acid and their corresponding LUS and β-AS gene expression were very low in 1-year old birch. With increasing age of birch, betulin content was increased, while oleanolic acid was decreased. Similar changes were also observed for their corresponding synthesis genes LUS and β-AS. In the leaf of 1-year old plant, the highest expression of CAS1 and CAS2 occurred at end of September, while expression of LUS and the β-AS was low from June to October. In the stem skin,high expression of β-AS and the LUS genes occurred from the end of July to September. In the root, high expression of the β-AS gene was observed at the end of October. These results indicated that triterpenoid gene expression was similar to the triterpene accumulation. Expression of LUS gene and β-AS gene in birch with different ages were corresponding to the betulinic and oleanolic acid accumulation. Expression of CAS1 and CAS2 genes were elevated with increasing age of birch. This study provides molecular mechanisms of triterpenes synthesis in birch plants.
白桦中桦木醇和齐墩果酸（五环三萜次生代谢物）的积累和分布特征及其相关基因的表达分析
桦木醇和齐墩果酸具有广泛的药理活性，可潜在用于开发抗癌和抗艾滋病药物。在这项研究中，我们检测了不同年龄白桦中桦木醇和齐墩果酸在各器官中的积累和分布特征。我们还通过实时 RT-PCR 测定了参与三萜合成途径的 4 个 OSC 基因（LUS、β-AS、CAS1 和 CAS2）的表达。结果表明，1 年生白桦能够合成桦木醇和齐墩果酸。此外，桦木醇和齐墩果酸主要分布在树皮中，而在根皮和叶片中的含量非常低。白桦中桦木醇和齐墩果酸的含量在不同季节有所变化。1 年生白桦中桦木醇和齐墩果酸及其相应的 LUS 和 β-AS 基因表达水平均较低。随着白桦年龄的增加，桦木醇的含量增加，而齐墩果酸的含量降低。其相应的合成基因 LUS 和 β-AS 也发生了类似的变化。在 1 年生植物叶片中，CAS1 和 CAS2 的表达在 9 月底达到最高，而 LUS 和 β-AS 的表达从 6 月到 10 月较低。在茎皮中，β-AS 和 LUS 基因的高表达发生在 7 月底至 9 月初。在根中，β-AS 基因的高表达发生在 10 月底。这些结果表明，三萜基因表达与三萜积累相似。不同年龄白桦中 LUS 基因和 β-AS 基因的表达与桦木醇和齐墩果酸的积累相对应。随着白桦年龄的增加，CAS1 和 CAS2 基因的表达增加。本研究为白桦植物三萜合成的分子机制提供了依据。
