气态植物激素——乙烯是植物生长过程的主要操控者。最为人熟知的是它的果实催熟功能。乙烯还能够诱导种子萌发和保护植物抵抗病原菌和环境压力。然而这种激素却引起切花产业和农业的重大损失。由加速植物腐烂的信号产生的乙烯，在加速果实成熟的同时也引起它们变质。在切花运输和处理过程中，乙烯诱导了花朵的提前凋谢。
近年来，科学家对于细胞内乙烯信号有了很多了解。美国Salk研究所的研究人员如今鉴定出乙烯响应的重要调节子——EIN2的功能。以前的研究一直没能阐明EIN2在乙烯信号通路中的作用。
Salk研究所的Joseph Ecker科学小组发现，乙烯的存在，使“短命”的EIN2可以聚集到足够浓度来传递乙烯信号。如果没有乙烯，一种CTR1蛋白将与EIN2结合抑制乙烯通路。一旦乙烯与其受体结合，EIN2将被激活。但是EIN2的激活机制仍不清楚。但已知有两个F-box蛋白：ETP1和ETP2，介导EIN2的降解。 乙烯的存在使这两个蛋白失活，因此EIN2不再被降解。
“这类调控好比把脚同时踩在油门和刹车上，然后慢抬刹车”Ecker解释说，“这能使细胞对接下来的信息立即作出响应。”这一发现还可能有利于改良植物对病原体和干旱的抗性。（生物谷Bioon.com）
生物谷推荐原始出处：
Genes & Dev.February 4, 2009, doi:10.1101/gad.1765709
Interplay between ethylene, ETP1/ETP2 F-box proteins, and degradation of EIN2 triggers ethylene responses in Arabidopsis
Hong Qiao, Katherine N. Chang, Junshi Yazaki and Joseph R. Ecker,1
Plant Biology Laboratory, The Salk Institute for Biological Studies, La Jolla, California 92037, USA
Abstract
The gaseous plant hormone ethylene can trigger myriad physiological and morphological responses in plants. While many ethylene signaling pathway components have been identified and characterized, little is known about the function of the integral membrane protein ETHYLENE-INSENSITIVE2 (EIN2), a central regulator of all ethylene responses. Here, we demonstrate that Arabidopsis thaliana EIN2 is a protein with a short half-life that undergoes rapid proteasome-mediated protein turnover. Moreover, EIN2 protein accumulation is positively regulated by ethylene. We identified two F-box proteins, EIN2 TARGETING PROTEIN1 (ETP1) and EIN2 TARGETING PROTEIN2 (ETP2), that interact with the EIN2 C-terminal domain (EIN2-CEND), which is highly conserved and sufficient to activate most ethylene responses. Overexpression of ETP1 or ETP2 disrupts EIN2 protein accumulation, and these plants manifest a strong ethylene-insensitive phenotype. Furthermore, knocking down the levels of both ETP1 and ETP2 mRNAs using an artificial microRNA (amiRNA) leads to accumulation of EIN2 protein, resulting in plants that display constitutive ethylene response phenotypes. Finally, ethylene down-regulates ETP1 and ETP2 proteins, impairing their ability to interact with EIN2. Thus, these studies reveal that a complex interplay between ethylene, the regulation of ETP1/ETP2 F-box proteins, and subsequent targeting and degradation of EIN2 is essential for triggering ethylene responses in plants.
