title: Cucumber mosaic virus movement protein severs actin filaments to increase the plasmodesmal size exclusion limit in tobacco.
abstract: Plant viral movement proteins (MPs) enable viruses to pass through cell walls by increasing the size exclusion limit (SEL) of plasmodesmata (PD). Here, we report that the ability of Cucumber mosaic virus (CMV) MP to increase the SEL of the PD could be inhibited by treatment with the actin filament (F-actin)-stabilizing agent phalloidin but not by treatment with the F-actin-destabilizing agent latrunculin A. In vitro studies showed that CMV MP bound globular and F-actin, inhibited actin polymerization, severed F-actin, and participated in plus end capping of F-actin. Analyses of two CMV MP mutants, one with and one without F-actin severing activities, demonstrated that the F-actin severing ability was required to increase the PD SEL. Furthermore, the Tobacco mosaic virus MP also exhibited F-actin severing activity, and its ability to increase the PD SEL was inhibited by treatment with phalloidin. Our data provide evidence to support the hypothesis that F-actin severing is required for MP-induced increase in the SEL of PD. This may have broad implications in the study of the mechanisms of actin dynamics that regulate cell-to-cell transport of viral and endogenous proteins.
authors.affiliation: State Key Laboratory of Plant Physiology and Biochemistry, Department of Plant Sciences, College of Biological Sciences, China Agricultural University, Beijing 100193, China.
authors.forename: Shengzhong
authors.initials: S
authors.lastname: Su
authors.forename: Zhaohui
authors.initials: Z
authors.lastname: Liu
authors.forename: Cheng
authors.initials: C
authors.lastname: Chen
authors.forename: Yan
authors.initials: Y
authors.lastname: Zhang
authors.forename: Xu
authors.initials: X
authors.lastname: Wang
authors.forename: Lei
authors.initials: L
authors.lastname: Zhu
authors.forename: Long
authors.initials: L
authors.lastname: Miao
authors.forename: Xue-Chen
authors.initials: XC
authors.lastname: Wang
authors.forename: Ming
authors.initials: M
authors.lastname: Yuan
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000199:Actins / Q000378:metabolism; D017799:Cucumovirus / Q000502:physiology*; D010590:Phalloidine / Q000494:pharmacology; D010935:Plant Diseases / Q000821:virology*; D053830:Plant Viral Movement Proteins / Q000378:metabolism*; D031425:Plasmodesmata / Q000378:metabolism; D014026:Nicotiana / Q000821:virology*
chemical_list: D000199:Actins; D053830:Plant Viral Movement Proteins; D010590:Phalloidine