Gibberellin Is Essentially Required for Carrot (<i>Daucus carota</i>L.) Somatic Embryogenesis: Dynamic Regulation of Gibberellin 3-Oxidase Gene Expressions
作者:Wataru MITSUHASHI、Tomonobu TOYOMASU、Hiroyuki MASUI、Toshinori KATHO、Kentaro NAKAMINAMI、Yoshiko KASHIWAGI、Mitsuaki AKUTSU、Hiromichi KENMOKU、Takeshi SASSA、Shinjiro YAMAGUCHI、Yuji KAMIYA、Hiroshi KAMADA
DOI:10.1271/bbb.67.2438
日期:2003.1
A GA biosynthesis inhibitor, uniconazole, caused many shrunken embryos when it was supplied to cultured carrot (Daucus carota L.) cells at the induction of somatic embryos. The abnormality was prevented by exogenous GA1 or GA4. To analyze the status of GA biosynthesis during somatic embryogenesis, expression patterns of newly isolated genes encoding GA biosynthetic enzymes, two GA 20-oxidases, three GA 3-oxidases, and two GA 2-oxidases were observed by using a semi-quantitative reverse-transcription-polymerase chain reaction with gene-specific primers. Transcript levels of GA 20-oxidases and GA 2-oxidases did not change greatly during development of the somatic embryo. On the other hand, drastic changes were found in three GA 3-oxidase genes. Strikingly, expression of a GA 3-oxidase gene, DcGA3ox2, was elevated once in somatic embryogenesis, but not in the non-induced suspension cells. The enzymatic functions of these gene products were also confirmed using recombinant proteins expressed in Escherichia coli. Our results indicate that GA biosynthesis is required for carrot somatic embryogenesis.
在诱导体细胞胚胎时,向培养的胡萝卜(Daucus carota L.)细胞提供一种 GA 生物合成抑制剂--烯效唑,会导致许多胚胎萎缩。外源 GA1 或 GA4 可防止这种异常现象。为了分析体细胞胚胎发生过程中GA生物合成的状况,使用基因特异性引物进行半定量反转录聚合酶链反应,观察了新分离的编码GA生物合成酶的基因、2个GA 20-氧化酶、3个GA 3-氧化酶和2个GA 2-氧化酶的表达模式。在体细胞胚胎发育过程中,GA 20-氧化酶和 GA 2-氧化酶的转录水平变化不大。另一方面,在三个 GA 3- 氧化酶基因中发现了剧烈的变化。令人吃惊的是,在体细胞胚胎发育过程中,GA 3-氧化酶基因 DcGA3ox2 的表达一度升高,但在非诱导悬浮细胞中却没有升高。用大肠杆菌表达的重组蛋白也证实了这些基因产物的酶功能。我们的研究结果表明,胡萝卜体细胞胚胎发生需要 GA 的生物合成。