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Journal of Integrative Agriculture
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The Nicotiana benthamiana microtubule-associated E3 ubiquitin ligase degrades a host immune regulator and a viral effector to enhance antiviral defense

Kun Wang1, Shuai Fu1, Yuchong Tan1, Liang Wu1, Yaqin Wang1#, Xueping Zhou1,2#

State Key Laboratory of Rice Biology, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou 310058, China

State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing 100193, China 

 Highlights 

· Geminivirus infection activates the upregulation expression of plant microtubule-associated E3 ligase (MEL).

· MEL promotes the degradation of plant immune negative regulator to resist geminivirus.

· MEL specifically recognizes geminivirus-encoded effector V2 protein for poly-ubiquitination and degradation.

· Geminivirus infection activates the upregulation expression of plant microtubule-associated E3 ligase (MEL).

· MEL promotes the degradation of plant immune negative regulator to resist geminivirus.

· MEL specifically recognizes geminivirus-encoded effector V2 protein for poly-ubiquitination and degradation. -->

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摘要  

【目的】双生病毒主要侵染双子叶植物并造成严重的产量损失,实验室前期鉴定并解析了一个单子叶植物水稻中微管相关的E3连接酶microtubule-associated E3 ligase OsMEL)及其调控水稻条纹病毒(rice stripe virus, RSV)侵染的机制。本研究通过解析双子叶植物本氏烟中微管相关的E3连接酶NbMEL调控双生病毒侵染的分子机制,为在双子叶植物中利用MEL抗病育种提供理论依据。

【方法】通过在野生型本氏烟上接种不同的双生病毒,运用实时荧光定量PCR检测不同双生病毒侵染后NbMEL表达量变化;在NbMELNbSHMT1转基因植株上接种不同的双生病毒后检测病毒积累量及植物免疫反应变化,分析NbMEL-NbSHMT1模块在调控双生病毒侵染中的作用;利用体内蛋白稳定性试验分析E3连接酶NbMEL对双生病毒编码的多个蛋白的积累量影响;运用酵母双杂交(Y2H)及双分子荧光互补(BiFC)试验分析NbMEL与双生病毒编码蛋白的互作情况;结合体内及体外泛素化试验,检测E3连接酶NbMEL对双生病毒编码蛋白的泛素化修饰情况。

【结果】利用实时荧光定量PCR检测发现多个双生病毒分别接种本氏烟后均能激活NbMEL上调表达;进一步在NbMELNbSHMT1转基因植株上接种不同的双生病毒后检测病毒积累量及植物免疫反应发现,NbMEL-NbSHMT1模块通过调控植物免疫反应从而抑制双生病毒侵染;通过分析E3连接酶NbMEL对双生病毒编码的多个蛋白的积累量影响,结果显示NbMEL能够特异性促进双生病毒编码的V2蛋白降解;结合酵母双杂交(Y2H)及双分子荧光互补(BiFC)试验分析发现,NbMEL能够与多个双生病毒编码的V2蛋白互作。体内及体外泛素化试验和蛋白降解试验结果显示,E3连接酶NbMEL能够促进双生病毒编码的V2蛋白发生体外及体内泛素化修饰并通过26S蛋白酶体通路降解。

【结论】本氏烟E3连接酶NbMEL在调控双生病毒侵染过程中发挥双重作用:一方面通过降解免疫负调控因子SHMT1从而激活SHMT1下游介导的植物防卫反应抵抗病毒侵染;另一方面,NbMEL直接靶向双生病毒编码的V2蛋白,通过促使V2蛋白发生多聚泛素化修饰从而通过26S蛋白酶体通路降解

【创新性】本研究揭示了双子叶植物E3连接酶MEL在调控双生病毒侵染过程中双重作用,为在双子叶植物中利用MEL抗病育种提供理论依据。

 



Abstract  

Geminiviruses mainly infect economically important dicot plants and cause serious damages in agriculture. Here we report that the dicot plant Nicotiana benthamiana microtubule-associated E3 ligase (MEL) plays a dual role in regulating geminivirus infection in N. benthamiana. On the one hand, NbMEL functioned as a defense factor to mediate resistance against geminiviruses with single-stranded, circular DNA genomes by promoting the degradation of plant immune negative regulator. On the other hand, NbMEL could specifically recognize geminivirus-encoded V2 protein, a viral gene silencing suppressor and effector, for polyubiquitination and degradation to suppress geminivirus infection. These findings provide a fundamental basis for utilizing MEL to generate crop for broad-spectrum resistance in dicot plants.

Keywords:  Microtubule-associated E3 ligase       ubiquitination        SHMT1        defense response        geminivirus        V2  
Online: 01 November 2025  
Fund: 

This research was supported by grants from the National Natural Science Foundation of China (32372480 and W2411024). 

About author:  #Correspondence Yaqin Wang, E-mail: yaqinwang@zju.edu.cn; Xueping Zhou, E-mail: zzhou@zju.edu.cn

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Kun Wang, Shuai Fu, Yuchong Tan, Liang Wu, Yaqin Wang, Xueping Zhou. 2025. The Nicotiana benthamiana microtubule-associated E3 ubiquitin ligase degrades a host immune regulator and a viral effector to enhance antiviral defense. Journal of Integrative Agriculture, Doi:10.1016/j.jia.2025.10.022

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