Gibberellin (GA) 20-oxidase (GA20ox) is a key enzyme that normally catalyzes the penultimate steps in GA biosynthesis. One of the GA20ox genes in rice (Oryza sativaL.), OsGA20ox2 (SD1), is well known as the 'Green Revolution gene', and loss-of function mutation in this locus causes semi-dwarfism. Another GA20ox gene, OsGA20ox1, has also been identified, but its contribution to plant stature has remained unclear because no suitable mutants have been available. We isolated a mutant, B142, tagged with a T-DNA containing three CaMV 35S promoters, which showed a tall, GA-overproduction phenotype. The final stature of the B142 mutant reflects internode overgrowth and is approximately twice that of its wild-type parent. This mutant responds to application of both GA
赤霉素20氧化酶(GA20ox)是催化GA生物合成倒數(shù)第二步反應(yīng)的關(guān)鍵酶。水稻GA20ox基因之一OsGA20ox2 (SD1)是人們所熟知的綠色革命基因，該基因功能喪失型突變導(dǎo)致株高半矮化。另外一個(gè)GA20ox基因OsGA20ox1也已經(jīng)被鑒定出來(lái)，但由于沒(méi)有得到合適的突變體該基因?qū)χ晷偷挠绊戇€不清楚。我們通過(guò)包含3個(gè)花椰菜病毒35S啟動(dòng)子的T-NDA標(biāo)簽分離到了一個(gè)株高變高GA含量增加的突變體B142。B142突變體的株型表現(xiàn)為節(jié)間過(guò)度伸長(zhǎng)，長(zhǎng)度大約為野生型的兩倍。該突變體對(duì)GA3和GA合成抑制劑都有響應(yīng)，說(shuō)明它不同于GA信號(hào)傳導(dǎo)突變體如slr1，是一個(gè)新的株高變高突變體。在B142突變體中，包含3個(gè)花椰菜病毒35S啟動(dòng)子的T-NDA標(biāo)簽插在OsGA20ox1開(kāi)放閱讀框的上游。mRNA和內(nèi)源GA含量測(cè)定表明B142突變體中OsGA20ox1表達(dá)量上調(diào)，活性GA含量升高。將35S啟動(dòng)子驅(qū)動(dòng)OsGA20ox1 cDNA轉(zhuǎn)到野生型中出現(xiàn)與B142突變體一樣的表型。這些結(jié)果表明B142突變體節(jié)間伸長(zhǎng)的表型是由于OsGA20ox1表達(dá)上調(diào)造成。另外，特異抑制OsGA20ox1基因的表達(dá)使株高變矮，說(shuō)明不僅OsGA20ox2基因影響植物株型， OsGA20ox1基因也可以影響植物株型。
結(jié)果：B142突變體的分離和鑒定。 B142突變體對(duì)GA和GA合成抑制劑的響應(yīng)。 T-DNA在突變體基因組中的插入位點(diǎn)。 B142突變體中OsGA20ox1的表達(dá)上調(diào)，活性GA含量升高。 過(guò)量表達(dá)OsGA20ox1的轉(zhuǎn)基因植株出現(xiàn)與B142突變體類(lèi)似的表型。 特異抑制OsGA20ox1基因的表達(dá)導(dǎo)致株高半矮化。