Topolins and Hydroxylated Thidiazuron Derivatives Are Substrates of Cytokinin O-Glucosyltransferase with Position Specificity Related to Receptor Recognition1
Topolins and Hydroxylated Thidiazuron Derivatives Are Substrates of Cytokinin O-Glucosyltransferase with Position Specificity Related to Receptor Recognition1
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DOI：
10.1104/pp.104.057174
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发表时间：
2005-03
期刊：
影响因子：
7.4
通讯作者：
M. Mok;Ruth C. Martin;P. Dobrev;R. Vaňková;P. Shing Ho;K. Yonekura-Sakakibara;H. Sakakibara;D. M
中科院分区：
文献类型：
--
作者：
M. Mok;Ruth C. Martin;P. Dobrev;R. Vaňková;P. Shing Ho;K. Yonekura-Sakakibara;H. Sakakibara;D. M
反式玉米素的葡萄糖苷广泛存在于植物组织中，通过羟基化侧链的O-葡萄糖基化或嘌呤环结构的N-葡萄糖基化形成。O-葡萄糖基化是立体特异性的：由Phaseolus lunatus ZOG 1基因编码的O-葡萄糖基转移酶对作为底物的反式玉米素具有高亲和力，而由玉米（Zea mays）cisZOG 1基因编码的酶偏好顺式玉米素。在这里，我们表明，苄基腺嘌呤（topolins）的羟基化衍生物也是ZOG 1和cisZOG 1的底物。m-OH和o-OH衍生物分别是ZOG 1和cisZOG 1的优选底物。在所测试的噻苯隆的羟基化衍生物中，导致转化的唯一酶/底物组合是cisZOG 1/（o-OH）噻苯隆。这些细胞分裂素作为葡萄糖基转移酶的底物的能力在很大程度上与它们在月斑紫菜愈伤组织生物测定中的生物活性相关，表明酶和细胞分裂素受体上的细胞分裂素结合位点之间可能存在相似性。涉及拟南芥（Arabidopsis thaliana）CRE 1/WOL/AHK 4和玉米ZmHK 1受体的细胞分裂素识别研究提供了对这种解释的进一步支持。AHK 4受体对反式玉米素和间托泊林有反应，而ZmHK 1受体也对顺式玉米素和邻托泊林有反应。三维分子模型的基板被施加到解释的结果。
Glucosides of trans-zeatin occur widely in plant tissues, formed either by O-glucosylation of the hydroxylated side chain or N-glucosylation of the purine ring structure. O-Glucosylation is stereo-specific: the O-glucosyltransferase encoded by the Phaseolus lunatus ZOG1 gene has high affinity for trans-zeatin as the substrate, whereas the enzyme encoded by the maize (Zea mays) cisZOG1 gene prefers cis-zeatin. Here we show that hydroxylated derivatives of benzyladenine (topolins) are also substrates of ZOG1 and cisZOG1. The m-OH and o-OH derivatives are the preferred substrate of ZOG1 and cisZOG1, respectively. Among the hydroxylated derivatives of thidiazuron tested, the only enzyme/substrate combination resulting in conversion was cisZOG1/(o-OH) thidiazuron. The abilities of these cytokinins to serve as substrates to the glucosyltransferases were in a large part correlated with their biological activities in the P. lunatus callus bioassay, indicating that there may be similarities between cytokinin-binding sites on the enzymes and cytokinin receptors. Further support for this interpretation is provided by cytokinin recognition studies involving the Arabidopsis (Arabidopsis thaliana) CRE1/WOL/AHK4 and maize ZmHK1 receptors. The AHK4 receptor responded to trans-zeatin and m-topolin, while the ZmHK1 receptor responded also to cis-zeatin and o-topolin. Three-dimensional molecular models of the substrates were applied to explain the results.