Function and transcript analysis of gibberellin-biosynthetic enzymes in wheat
Function and transcript analysis of gibberellin-biosynthetic enzymes in wheat
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DOI：
10.1007/s00425-005-0104-0
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发表时间：
2006-02-01
期刊：
影响因子：
4.3
通讯作者：
Hedden, P
中科院分区：
文献类型：
--
作者：
Appleford, NEJ;Evans, DJ;Hedden, P
赤霉素 (GA) 20-氧化酶和 3-氧化酶是 GA 生物合成的主要调节位点。我们已经鉴定了编码这些酶的每个基因家族的一个成员，这些酶在伸长的茎以及发育和发芽的小麦籽粒中高度表达，因此可能在这些组织中具有显着的发育作用。我们将 GA 20-氧化酶基因 TaGA20ox1 的三个同源物定位到染色体 5BL、5DL 和 4AL。 TaGA20ox1 主要在伸长茎的节和穗中表达，也在发育和发芽的胚胎中表达。节、穗和发芽胚胎中的表达主要来自 A 和 D 基因组。每个同源 cDNA 都编码一种功能酶，可催化 GA(12)-GA(9) 和 GA(53)-GA(20) 的多步转化。时程和酶动力学研究表明，从 GA(12) 和 GA(53) 分别到游离醇形式 GA(15) 和 GA(44) 的初始氧化步骤发生得很快，但后续步骤发生得更慢。中间体 GA(19) 对酶的亲和力特别低，这与它在小麦组织中的积累一致。 3-氧化酶基因 TaGA3ox2 的三个同源 cDNA 编码功能酶，其中一种除了 3β-羟化酶活性外，还具有低水平的 2β-羟化酶、2,3-去饱和酶、2,3-环氧化酶甚至 13-羟化酶活性。与 TaGA20ox1 相比，TaGA3ox2 在节间以及伸长茎的节和穗中表达。它在发育和发芽的胚胎中也高度表达。
The enzymes gibberellin (GA) 20-oxidase and 3-oxidase are major sites of regulation in GA biosynthesis. We have characterised one member of each of the gene families encoding these enzymes that are highly expressed in elongating stems and in developing and germinating grains of wheat and are therefore likely to have prominent developmental roles in these tissues. We mapped the three homoeologues of the GA 20-oxidase gene TaGA20ox1 to chromosomes 5BL, 5DL and 4AL. TaGA20ox1 is expressed mainly in the nodes and ears of the elongating stem, and also in developing and germinating embryos. Expression in the nodes, ears and germinating embryos is predominantly from the A and D genomes. Each homoeologous cDNA encodes a functional enzyme that catalyses the multi-step conversions of GA(12)-GA(9), and GA(53)-GA(20). Time course and enzyme kinetic studies indicate that the initial oxidation steps from GA(12) and GA(53) to the free alcohol forms of GA(15) and GA(44), respectively, occur rapidly but that subsequent steps occur more slowly. The intermediate GA(19) has an especially low affinity for the enzyme, consistent with its accumulation in wheat tissues. The three homoeologous cDNAs for the 3-oxidase gene TaGA3ox2 encode functional enzymes, one of which was shown to possess low levels of 2 beta-hydroxylase, 2,3-desaturase, 2,3-epoxidase and even 13-hydroxylase activities in addition to 3 beta-hydroxylase activity. In contrast to TaGA20ox1, TaGA3ox2 is expressed in internodes, as well as nodes and the ear of the elongating stem. It is also highly expressed in developing and germinated embryos.