[原生質絲] 除了癒創聚葡糖（callose）外，調控原生質絲通透性的另一個機制？ 20191010 PNAS

Salicylic acid-mediated plasmodesmal closure via Remorin-dependent lipid organization

Dingquan Huang, Yanbiao Sun, Zhiming Mac, Meiyu Ke, Yong Cui, Zichen Chen, Chaofan Chen, Changyang Ji, Tuan Minh Tran, Liang Yang, Sin Man Lam, Yanhong Han, Guanghou Shu, Jirí Friml, Yansong Miao, Liwen Jiang, and Xu Chen

Abstract

Plasmodesmata (PD) are plant-specific membrane-lined channels that create cytoplasmic and membrane continuities between adjacent cells, thereby facilitating cell–cell communication and virus movement. Plant cells have evolved diverse mechanisms to regulate PD plasticity in response to numerous environmental stimuli. In particular, during defense against plant pathogens, the defense hormone, salicylic acid (SA), plays a crucial role in the regulation of PD permeability in a callose-dependent manner. Here, we uncover amechanism by which plants restrict the spreading of virus and PD cargoes using SA signaling by increasing lipid order and closure of PD. We showed that exogenous SA application triggered the compartmentalization of lipid raft nanodomains through a modulation of the lipid raftregulatory protein, Remorin (REM). Genetic studies, superresolution imaging, and transmission electron microscopy observation together demonstrated that Arabidopsis REM1.2 and REM1.3 are crucial for plasma membrane nanodomain assembly to control PD aperture and functionality. In addition, we also found that a 14-3-3 epsilon protein modulates REM clustering and membrane nanodomain compartmentalization through its direct interaction with REM proteins. This study unveils a molecular mechanism by which the key plant defense hormone, SA, triggers membrane lipid nanodomain reorganization, thereby regulating PD closure to impede virus spreading.

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水楊酸經由調控Remorin蛋白來組織脂質而影響原生質絲的關閉

摘要

原生質絲是植物所特有，具有生物膜，而連接細胞間細胞質與細胞膜連續性的通道。藉此通道，植物可以促進細胞間的溝通，然而病毒也會利用此通道而加速傳遞。植物演化出了許多針對不同外界環境刺激的應對機制來調控原生質斯的通透性。尤其是當有病原體入侵時，防禦荷爾蒙 - 水楊酸會經由一個獨立於癒創聚葡糖調控外的調控機制來關閉原生質絲。我們在這篇研究中發現了，植物會利用水楊酸的訊息傳遞，來增加之值得規律以關閉原生質斯，進而避免病毒的擴散。我們發現，外加水楊酸會透過一個可以調控脂質組成聚合區域的蛋白質 - Remorin（REM）來刺激細胞膜上脂質區域形成聚合區域。透過遺傳學、超解析度影像分析、以及穿透式電子顯微鏡的觀察，我們展示了，阿拉伯芥中 REM1.2以及REM1.3對於細胞膜上脂質形成奈米大小的聚合區塊，進而調控原生質絲的開闔與功能，有很重要的影響。此外，我們也發現了一個14-3-3蛋白可直接與REM互動，調節REM的聚合以及細胞膜上奈米區域的生成。這個研究揭示了主要的植物防禦荷爾蒙 - 水楊酸調節細胞膜上奈米區塊的組成來閉合原生質絲，最終避免病毒擴散的分子機制。