拟南芥两个E3连接酶通过调节NADPH氧化酶调控细胞分裂素信号

NADPH oxidases (NOX) are the enzymes that generate reactive oxygen species (ROS). In plants, NOX (also termed Rboh) have been reported to be involved in various physiological processes, such as cell growth, development and responses to environmental stresses. Cytokinin is one of the most important phytohormones regulating plants growth and development by promoting cell proliferation, differentiation and other cellular processes. Very few studies have been reported so far linking ROS and cytokinin signaling although both of them have been well-studied. Our previous work indicated that two E3 ligases PUB2 and PUB4 contribute to cytokinin responses. Recently, PUB2 and PUB4 were found to directly interact with RbohD and is involved in ROS production in our lab. It is likely that PUB2/4 might interact with Rboh proteins and ubiquitin them, resulting in modulation of the NADPH oxidases activity. We will test whether PUB2/4 might regulate NOX activity through mono-ubiquitination and whether ROS production by such an action functions in cytokinin responses. Our study will provide new insights into roles of ROS in plant growth，development and stress responses.

NADPH氧化酶(NOX)是一种被广泛研究的能够催化产生活性氧的酶，研究表明NOX在植物中参与生长发育以及应对环境胁迫等多种生理学过程。细胞分裂素是重要的植物激素，它通过促进细胞分裂、分化等过程参与植物生长发育等方面的调控。尽管关于活性氧信号和细胞分裂素信号都已经取得大量的研究成果，它们之间的关系却鲜有研究。我们的研究表明拟南芥两个E3 连接酶PUB2和PUB4调控细胞分裂素信号。它们可以直接与NOX互作，调节活性氧的产生。我们将探讨PUB2/4是否通过泛素化来调节NOX的活性，从而调控细胞分裂素信号转导过程,这将为我们进一步了解植物生长发育调节、胁迫应答提供新的视角。

NADPH氧化酶在植物生长发育，对生物胁迫以及非生物胁迫应答都起着重要作用。我们的研究表明两个E3连接酶PUB2和PUB4参与调控植物对生物胁迫下活性氧的产生。研究表明PUB2/4直接与多个NADPH氧化酶互作。而PUB4的泛素化活性对PAMP诱导下的活性氧的产生不是必需的，而ARM重复结构域是PUB4功能所必需。进一步的研究表明PUB2和PUB4可能行使支架蛋白的功能，通过促进FLS2与BIK1和BIK1与RbohD之间的互作调控活性氧的产生。在活性氧和细胞分裂素两者关系的研究中我们发现，目前我们没有足够的证据证明活性氧能直接促进细胞分裂素信号。本研究揭示了活性氧产生的新的分子机制，以及E3泛素化连接酶蛋白独立于E3连接酶活性的功能。