Uncertainty of EIN2^(Ser645/Ser924) Inactivation by CTR1-Mediated Phosphorylation Reveals the Complexity of Ethylene Signaling  

作　　者：Jingyi Zhang Yuying Chen Jian Lu Ying Zhang Chi-Kuang Wen 

机构地区：[1]National Key Laboratory of Plant Molecular Genetics,CAS Center for Excellence in Molecular Plant Sciences,Institute of Plant Physiology and Ecology,Chinese Academy of Sciences,Shanghai 200032,China

出　　处：《Plant Communications》2020年第3期57-74,共18页植物通讯（英文）

基　　金：supported by the National Natural Science Foundation of China(31570277 and 31770302);Chinese Academy of Sciences(XDB27030208).

摘　　要：ETHYLENE INSENSITIVE2(EIN2)is a key component of ethylene signaling whose activity is inhibited upon phosphorylation of Ser^(645) and Ser^(924) by the Raf-like CONSTITUTIVE TRIPLE-RESPONSE 1(CTR1)in the absence of ethylene.Ethylene prevents CTR1 activity and thus EIN2^(Ser645/Ser924) phosphorylation,and subcellular trafficking of a proteolytically cleaved EIN2 C terminus(EIN2-C)from the endoplasmic reticulum to the nucleus and processing bodies triggers ethylene signaling.Here,we report an unexpected complexity of EIN2-activated ethylene signaling.EIN2 activation in part requires ethylene in the absence of CTR1-mediated negative regulation.The ein2 mutant was complemented by the transgenes encoding EIN2,EIN2 variants with mutations that either prevent or mimic Ser^(645)/Ser^(924) phosphorylation,or EIN2-C;and all the transgenic lines carrying these EIN2-derived transgenes responded to ethylene.Furthermore,we found that the fluorescence protein-tagged EIN2 and its variants were affected little by ethylene and exhibited similar subcellular distribution patterns:in the cytosolic particles and nuclear speckles.Of note,the subcellular localization patterns of EIN2 proteins fused with a fluorescence protein either at the N or C terminus were similar,whereas EIN2-C-YFP was primarily observed in the cytosol but not in the nucleus.Western blots and mass spectrum analyses suggested a high complexity of EIN2,which is likely proteolytically processed into multiple fragments.Our results suggested a nuclear localization of the full-length EIN2,weak association of the EIN2^(Ser645/Ser924) phosphorylation status and ethylene signaling,and the complexity of ethylene signaling caused by EIN2 and its proteolytic products in different subcellular compartments.We propose an alternative model to explain EIN2-activated ethylene signaling.

关 键 词：ethylene signaling EIN2 phosphorylation EIN2 complexity CTR1 ETR1 

分 类 号：Q94[生物学—植物学]