细胞分裂素参与调控植物生长发育中几乎所有重要过程。细胞分裂素信号转导是通过一个连续磷酸传递（phosphorelay）而介导的。在拟南芥中，被细胞分裂素激活的受体自磷酸化后，将磷酸基团传递至磷酸转移蛋白（AHP），并进一步传递至下游的反应调节子（ARR）。对细胞分裂素信号转导中调节机制，特别是对磷酸传递的调节机制了解很少。
中国科学院遗传与发育生物学研究所左建儒研究组与中国科学院动物研究所李晓明博士的合作研究发现一氧化氮负调控细胞分裂素信号转导。一氧化氮的一个主要生化功能是对蛋白质特异半胱氨酸残基的巯基进行S-亚硝基化修饰。S-亚硝基化修饰是一种基于氧化还原的蛋白质翻译后修饰机制。与磷酸化等蛋白质翻译后修饰机制类似，S-亚硝基化修饰参与调控其靶蛋白的生物学活性。左建儒研究组发现S-亚硝基化修饰细胞分裂素信号通路的重要组分AHP1后，抑制AHP1及其下游组分ARR1的磷酸化，从而负调控细胞分裂素信号转导以及植物对细胞分裂素的响应。该项研究为解析细胞分裂素信号通路感受氧化还原信号进而调控植物生长发育的机制提供了新线索。
该研究结果于2月26日在线发表于《自然—通讯》（Nature Communications）。左建儒研究组的冯健博士为论文的第一作者。该项研究得到了国家自然科学基金的资助。（生物谷Bioon.com）
doi:10.1038/ncomms2541
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S-nitrosylation of phosphotransfer proteins represses cytokinin signaling
Jian Feng, Chun Wang, Qingguo Chen, Hui Chen, Bo Ren, Xiaoming Li & Jianru Zuo
Cytokinin is an essential phytohormone in plant growth and development. In Arabidopsis, cytokinin signalling is mediated by a phosphorelay that sequentially transfers phosphoryl groups from the cytokinin receptors to histidine phosphotransfer proteins (AHPs) and response regulators (ARRs). However, little is known about the regulatory mechanism of the phosphorelay. Here, we show that nitric oxide negatively regulates cytokinin signalling by inhibiting the phosphorelay activity through S-nitrosylation. S-nitrosylation of AHP1 at Cys 115 represses its phosphorylation and subsequent transfer of the phosphoryl group to ARR1. A non-nitrosylatable mutation of AHP1 renders the mutant protein insensitive to nitric oxide in repressing its phosphorylation, and partially relieves the inhibitory effect of nitric oxide on the cytokinin response. Conversely, a nitrosomimetic mutation of AHP1 causes reduced phosphorylation of AHP1 and ARR1, thereby resulting in a compromised cytokinin response. These findings illustrate a mechanism by which redox signalling and cytokinin signalling coordinate plant growth and development.
