The involvement of cytokinin oxidase/dehydrogenase and zeatin reductase in regulation of cytokinin levels in pea (Pisum sativum L.) leaves
The involvement of cytokinin oxidase/dehydrogenase and zeatin reductase in regulation of cytokinin levels in pea (Pisum sativum L.) leaves
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DOI：
10.1007/s00344-005-0043-9
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发表时间：
2005-09-01
影响因子：
4.8
通讯作者：
Motyka, V
中科院分区：
文献类型：
--
作者：
Gaudinová, A;Dobrev, PI;Motyka, V
细胞分裂素在植物体内的代谢非常复杂。利用高效液相色谱-质谱联用技术（HPLC-MS）从豌豆（PisumsativumL.）中鉴定出20多种含类异戊二烯和芳香族侧链的细胞分裂素。CV. Gotik）叶，表明细胞分裂素生物合成的初级产物的多种代谢转化。为了确定代谢细胞分裂素的两种酶，细胞分裂素氧化酶/脱氢酶（CKX，EC 1.5.99.12）和玉米素还原酶（ZRED，EC 1.3.1.69），在内源性细胞分裂素水平的控制中的潜在参与，研究了它们与豌豆芽外植体中[2-H-3]反式玉米素（[2-H-3] Z）的摄取和代谢相关的体外活性。在2、5、8和24 h孵育期间，检测到反式玉米素9-核苷、反式玉米素9-核苷-5 '-单磷酸和细胞分裂素降解产物腺嘌呤和腺苷为主要的[2-H-3] Z代谢产物。腺嘌呤和腺苷形成的增加表明CKX广泛降解[2-H-3] Z。高CKX活性，证实了蛋白质制剂从豌豆叶，茎，根在体外测定。二硫苏糖醇（15 mM）对CKX的抑制在酶测定中显示了相对较高的ZRED催化Z转化为二氢玉米素（DHZ）的活性，并且在豌豆叶的蛋白质制剂中明显竞争相同的底物细胞分裂素（Z），而不是豌豆根和茎。豌豆叶酶将Z转化为DHZ是NADPH依赖性的，并且在体外被二乙基二硫代氨基甲酸（DIECA; 10 mM）显著抑制或完全抑制。本文讨论了CKX和ZRED在豌豆叶片细胞分裂素水平调控中的关系及其在植物细胞分裂素稳态建立和维持中的潜在作用。
Cytokinin metabolism in plants is very complex. More than 20 cytokinins bearing isoprenoid and aromatic side chains were identified by high performance liquid chromatography-mass spectrometry (HPLC-MS) in pea ( Pisum sativum L. cv. Gotik) leaves, indicating diverse metabolic conversions of primary products of cytokinin biosynthesis. To determine the potential involvement of two enzymes metabolizing cytokinins, cytokinin oxidase/dehydrogenase (CKX, EC 1.5.99.12) and zeatin reductase (ZRED, EC 1.3.1.69), in the control of endogenous cytokinin levels, their in vitro activities were investigated in relation to the uptake and metabolism of [2-H-3] trans- zeatin ([2-H-3] Z) in shoot explants of pea. Trans-zeatin 9-riboside, trans-zeatin 9-riboside-5'-monophosphate and cytokinin degradation products adenine and adenosine were detected as predominant [2-H-3] Z metabolites during 2, 5, 8, and 24 h incubation. Increasing formation of adenine and adenosine indicated extensive degradation of [2-H-3] Z by CKX. High CKX activity was confirmed in protein preparations from pea leaves, stems, and roots by in vitro assays. Inhibition of CKX by dithiothreitol ( 15 mM) in the enzyme assays revealed relatively high activity of ZRED catalyzing conversion of Z to dihydrozeatin (DHZ) and evidently competing for the same substrate cytokinin (Z) in protein preparations from pea leaves, but not from pea roots and stems. The conversion of Z to DHZ by pea leaf enzyme was NADPH dependent and was significantly inhibited or completely suppressed in vitro by diethyldithiocarbamic acid ( DIECA; 10 mM). Relations of CKX and ZRED in the control of cytokinin levels in pea leaves with respect to their potential role in establishment and maintenance of cytokinin homeostasis in plants are discussed.