Dual targeting of a virus movement protein to ER and plasma membrane subdomains is essential for plasmodesmata localization

PLoS Pathogens

Kazuya Ishikawa¹  Hiroaki Koinuma¹  Masayoshi Hashimoto¹  Yugo Kitazawa¹  Akira Yusa¹  Osamu Netsu¹  Yasuyuki Yamaji¹  Shigetou Namba¹ 

[1] Laboratory of Plant Pathology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, Japan

关键词: Anilines;    Fluorescence imaging;    Signal peptides;    Yellow fluorescent protein;    Immunoprecipitation;    Cell fusion;    Chaperone proteins;    Plasmodesmata;   

DOI  :  10.1371/journal.ppat.1006463

学科分类：生物科学（综合）

来源: Public Library of Science

【 摘 要 】

Plant virus movement proteins (MPs) localize to plasmodesmata (PD) to facilitate virus cell-to-cell movement. Numerous studies have suggested that MPs use a pathway either through the ER or through the plasma membrane (PM). Furthermore, recent studies reported that ER-PM contact sites and PM microdomains, which are subdomains found in the ER and PM, are involved in virus cell-to-cell movement. However, functional relationship of these subdomains in MP traffic to PD has not been described previously. We demonstrate here the intracellular trafficking of fig mosaic virus MP (MPFMV) using live cell imaging, focusing on its ER-directing signal peptide (SPFMV). Transiently expressed MPFMV was distributed predominantly in PD and patchy microdomains of the PM. Investigation of ER translocation efficiency revealed that SPFMV has quite low efficiency compared with SPs of well-characterized plant proteins, calreticulin and CLAVATA3. An MPFMV mutant lacking SPFMV localized exclusively to the PM microdomains, whereas SP chimeras, in which the SP of MPFMV was replaced by an SP of calreticulin or CLAVATA3, localized exclusively to the nodes of the ER, which was labeled with Arabidopsis synaptotagmin 1, a major component of ER-PM contact sites. From these results, we speculated that the low translocation efficiency of SPFMV contributes to the generation of ER-translocated and the microdomain-localized populations, both of which are necessary for PD localization. Consistent with this hypothesis, SP-deficient MPFMV became localized to PD when co-expressed with an SP chimera. Here we propose a new model for the intracellular trafficking of a viral MP. A substantial portion of MPFMV that fails to be translocated is transferred to the microdomains, whereas the remainder of MPFMV that is successfully translocated into the ER subsequently localizes to ER-PM contact sites and plays an important role in the entry of the microdomain-localized MPFMV into PD.

【 授权许可】

CC BY