Characterization of Cytokinin and Adenine Transport in Arabidopsis Cell Cultures
Characterization of Cytokinin and Adenine Transport in Arabidopsis Cell Cultures
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DOI：
10.1104/pp.108.128454
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发表时间：
2008-12-01
期刊：
影响因子：
7.4
通讯作者：
Frommer, Wolf B.
中科院分区：
文献类型：
--
作者：
Cedzich, Anna;Stransky, Harald;Frommer, Wolf B.
细胞分裂素分布于血管系统，并通过受体介导的信号转导触发靶细胞的反应。信号的感知和转导可以发生在质膜或细胞质溶胶中。信号被胞外或胞内细胞分裂素氧化酶的作用终止。虽然放射性示踪剂已被用于研究植物细胞分裂素的运输和代谢，但对细胞分裂素运输的动力学特性知之甚少。为了提供一个参考数据集，利用放射性标记反式玉米素（tZ）对拟南芥（Arabidopsis thaliana）细胞培养进行摄取研究。tZ的摄取动力学是多相的，表明存在低亲和力和高亲和力的运输系统。质子载体羰基氰化物间氯苯腙是细胞分裂素摄取的有效抑制剂，与H+介导的摄取一致。其他生理性细胞分裂素，如异戊烯腺嘌呤和苄基氨基嘌呤，是tZ摄取的有效竞争者，而尿囊素则没有抑制作用。腺嘌呤竞争玉米素的摄取，表明细胞分裂素氧化酶的降解产物是通过相同的系统运输的。比较拟南芥幼苗对腺嘌呤和tZ的吸收，揭示了相似的吸收动力学。在细胞培养中确定的动力学特性和底物特异性与植物特异性嘌呤渗透酶家族成员在清除细胞外腺嘌呤的腺嘌呤运输中发挥作用的假设是一致的，此外，还可能参与低亲和力的细胞分裂素摄取。
Cytokinins are distributed through the vascular system and trigger responses of target cells via receptor-mediated signal transduction. Perception and transduction of the signal can occur at the plasma membrane or in the cytosol. The signal is terminated by the action of extra-or intracellular cytokinin oxidases. While radiotracer studies have been used to study transport and metabolism of cytokinins in plants, little is known about the kinetic properties of cytokinin transport. To provide a reference dataset, radiolabeled trans-zeatin (tZ) was used for uptake studies in Arabidopsis (Arabidopsis thaliana) cell culture. Uptake kinetics of tZ are multiphasic, indicating the presence of both low-and high-affinity transport systems. The protonophore carbonyl cyanide m-chlorophenylhydrazone is an effective inhibitor of cytokinin uptake, consistent with H+-mediated uptake. Other physiological cytokinins, such as isopentenyl adenine and benzylaminopurine, are effective competitors of tZ uptake, whereas allantoin has no inhibitory effect. Adenine competes for zeatin uptake, indicating that the degradation product of cytokinin oxidases is transported by the same systems. Comparison of adenine and tZ uptake in Arabidopsis seedlings reveals similar uptake kinetics. Kinetic properties, as well as substrate specificity determined in cell cultures, are compatible with the hypothesis that members of the plant-specific purine permease family play a role in adenine transport for scavenging extracellular adenine and may, in addition, be involved in low-affinity cytokinin uptake.