A phytoplasma effector acts as a ubiquitin-like mediator between floral MADS-box proteins and proteasome shuttle proteins
A phytoplasma effector acts as a ubiquitin-like mediator between floral MADS-box proteins and proteasome shuttle proteins
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DOI：
10.1093/plcell/koac062
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发表时间：
2022-03-02
期刊：
影响因子：
11.6
通讯作者：
Yamaji, Yasuyuki
中科院分区：
文献类型：
--
作者：
Kitazawa, Yugo;Iwabuchi, Nozomu;Yamaji, Yasuyuki
植物病原菌产生的叶原体是一种细菌效应子，它通过介导蛋白酶体穿梭蛋白而不是泛素与宿主蛋白的相互作用来降解宿主蛋白。一些效应子利用真核生物中保守的泛素-蛋白酶体系统来水解靶蛋白。蛋白酶体的利用机制主要是通过泛素与靶蛋白的相互作用来介导的。叶原蛋白是由致病植原体产生的蛋白质效应子家族，其在多种植物中将花转化为叶。在这里，我们提出了一个非经典的机制，涉及到蛋白酶体的叶芽作用，是不依赖于泛素。在辐射敏感性23（radiation-sensitive 23，RAD 23）穿梭蛋白的存在下，叶状蛋白诱导花MADS盒转录因子（MTFs）的蛋白酶体降解，该穿梭蛋白将泛素化蛋白募集到蛋白酶体中。细胞内定位分析显示，叶状体诱导MTF与RAD 23共定位。MTF/叶状体/RAD 23三元蛋白复合物不仅在植物中检测到，而且在体外的泛素的情况下，表明叶状体直接介导MTF和RAD 23之间的相互作用。一个赖氨酸少的非泛素化的叶状突诱导降解的MTF或MTF的赖氨酸少的突变体。此外，阐明了MTF/叶原体/RAD 23蛋白复合物的顺序形成方法，首先通过MTF/叶原体相互作用，然后通过RAD 23募集。Phyllogen识别MTF的进化上保守的四聚化区域和RAD 23的泛素相关结构域。我们的研究结果表明，叶状体功能模拟泛素作为MTF和RAD 23之间的调解人。
Phyllogen, a bacterial effector produced by pathogenic phytoplasma, targets host proteins for proteasomal degradation by mediating their interaction with proteasome shuttle proteins instead of ubiquitin.Plant pathogenic bacteria have developed effectors to manipulate host cell functions to facilitate infection. A certain number of effectors use the conserved ubiquitin-proteasome system in eukaryotic to proteolyze targets. The proteasome utilization mechanism is mainly mediated by ubiquitin interaction with target proteins destined for degradation. Phyllogens are a family of protein effectors produced by pathogenic phytoplasmas that transform flowers into leaves in diverse plants. Here, we present a noncanonical mechanism for phyllogen action that involves the proteasome and is ubiquitin-independent. Phyllogens induce proteasomal degradation of floral MADS-box transcription factors (MTFs) in the presence of RADIATION-SENSITIVE23 (RAD23) shuttle proteins, which recruit ubiquitinated proteins to the proteasome. Intracellular localization analysis revealed that phyllogen induced colocalization of MTF with RAD23. The MTF/phyllogen/RAD23 ternary protein complex was detected not only in planta but also in vitro in the absence of ubiquitin, showing that phyllogen directly mediates interaction between MTF and RAD23. A Lys-less nonubiquitinated phyllogen mutant induced degradation of MTF or a Lys-less mutant of MTF. Furthermore, the method of sequential formation of the MTF/phyllogen/RAD23 protein complex was elucidated, first by MTF/phyllogen interaction and then RAD23 recruitment. Phyllogen recognized both the evolutionarily conserved tetramerization region of MTF and the ubiquitin-associated domain of RAD23. Our findings indicate that phyllogen functionally mimics ubiquitin as a mediator between MTF and RAD23.