Virus-vector–host interactions during movement and transmission of Grapevine fanleaf virus
C. RITZENTHALER (1), C. Hemmer (2), K. Hliebieh (1), F. Berthold (1), C. Schmitt-Keichinger (1), O. Lemaire (3), S. Muyldermans (4), G. Demangeat (3). (1) IBMP CNRS, Strasbourg, France; (2) CNRS INRA, Strasbourg, France; (3) INRA, Colmar, France; (4) VUB VIB, Brussels, Belgium
<i>Grapevine fanleaf virus</i> (GFLV) is a nepovirus responsible of a severe grapevine degeneration observed in vineyards worldwide. GFLV is specifically transmitted from grape to grape by the ectoparasitic nematode <i>Xiphinema index</i>. GFLV moves from cell-to-cell via plasmodesmata as entire virions through viral encoded tubules that result from the self-assembly of the movement protein (MP). Structurally, GFLV is an icosahedral virus of 30 nm of diameter with a pseudo <i>T</i> = 3 symmetry composed of 60 identical subunits. In recent studies we have been able resolve the atomic structure of GFLV and identified surface-exposed structural motifs essential for GFLV transmission and movement. Rods shaped viruses generally accommodate the production of fluorescently labeled viral particles consisting of fluorescent protein (FP)-coat protein (CP) fusions. In contrast, icosahedral viruses such as GFLV are incompatible with such an approach probably due to steric hindrance that totally prevents virion formation and movement. To circumvent these limitations, we produced single-domain antibody fragments also named Nanobodies that specifically recognize GFLV. When fused to FP and expressed <i>in planta</i>, these so-called chromobodies act as biosensors compatible with the spatio-temporal visualization of viral particles during the different steps of the virus life cycle.
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