J. A. Garcia,2 and
1INRA, UMR BFP 1332, Equipe de Virologie, CS 20032, 33882 Villenave d'Ornon, France; 2Departamento de Genética Molecular de Plantas, Centro Nacional de Biotecnología (CNB-CSIC), Campus Universidad Autónoma de Madrid, 28049 Madrid, Spain
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Accepted 14 December 2013.
A unique feature shared by all plant viruses of the Potyviridae family is the induction of characteristic pinwheel-shaped inclusion bodies in the cytoplasm of infected cells. These cylindrical inclusions are composed of the viral-encoded cylindrical inclusion helicase (CI protein). Its helicase activity was characterized and its involvement in replication demonstrated through different reverse genetics approaches. In addition to replication, the CI protein is also involved in cell-to-cell and long-distance movements, possibly through interactions with the recently discovered viral P3N-PIPO protein. Studies over the past two decades demonstrate that the CI protein is present in several cellular compartments interacting with viral and plant protein partners likely involved in its various roles in different steps of viral infection. Furthermore, the CI protein acts as an avirulence factor in gene-for-gene interactions with dominant-resistance host genes and as a recessive-resistance overcoming factor. Although a significant amount of data concerning the potential functions and subcellular localization of this protein has been published, no synthetic review is available on this important multifunctional protein. In this review, we compile and integrate all information relevant to the current understanding of this viral protein structure and function and present a mode of action for CI, combining replication and movement.
© 2014 The American Phytopathological Society