title: Cauliflower mosaic virus is preferentially acquired from the phloem by its aphid vectors.
abstract: Cauliflower mosaic virus (CaMV) is transmitted in a non-circulative manner by aphids following the helper strategy. Helper proteins P2 and P3 act as a bridge between virions and the aphid cuticle. Electronic monitoring of aphid stylet activities (EPG technique), transmission tests and electron microscopy showed that CaMV is preferentially acquired from the phloem by its most common aphid vectors, Brevycorine brassicae and Myzus persicae. We also found that CaMV is semipersistently transmitted and that the rate of acquisition does not follow a typical bimodal curve. Instead, the virus could be acquired from non-phloem tissues at a low and fairly constant rate after one or more intracellular punctures within a few minutes, but the probability of acquisition rose significantly when aphids reached the phase of committed ingestion from the phloem. The acquisition rate of CaMV did not increase with increasing number of intracellular punctures, but the total duration of intracellular puncture was one of the variables selected by the stepwise logistic regression model used to fit the data that best explained acquisition of CaMV. Furthermore, aphids reaching the phloem faster had a higher probability of acquiring the virus. Our results support the hypothesis that multiple intracellular punctures of epidermal and mesophyll cells result in loading aphids with the CaMV-encoded aphid transmission factor (P2), and that aphids, in most cases, subsequently acquire CaMV particles during phloem sap ingestion. Consistently, immunoelectron microscopy showed that P3-virions are frequently found in the sieve element lumen, whereas P2 could not be detected.
authors.affiliation: Centro de Ciencias Medioambientales, CSIC, Serrano 115 dpo, 28006 Madrid, Spain1.
authors.forename: Itziar
authors.initials: I
authors.lastname: Palacios
authors.affiliation: Station de Recherches de Pathologie Comparée, INRA-CNRS-UM II, 30380 Saint Christol-les-Alès, France2.
authors.forename: Martin
authors.initials: M
authors.lastname: Drucker
authors.affiliation: Station de Recherches de Pathologie Comparée, INRA-CNRS-UM II, 30380 Saint Christol-les-Alès, France2.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Blanc
authors.affiliation: Centro de Ciencias Medioambientales, CSIC, Serrano 115 dpo, 28006 Madrid, Spain1.
authors.forename: Silvia
authors.initials: S
authors.lastname: Leite
authors.affiliation: Centro de Ciencias Medioambientales, CSIC, Serrano 115 dpo, 28006 Madrid, Spain1.
authors.forename: Aranzazu
authors.initials: A
authors.lastname: Moreno
authors.affiliation: Centro de Ciencias Medioambientales, CSIC, Serrano 115 dpo, 28006 Madrid, Spain1.
authors.forename: Alberto
authors.initials: A
authors.lastname: Fereres
mesh_terms: D000818:Animals; D001042:Aphids / Q000502:physiology / Q000821:virology*; D001937:Brassica / Q000033:anatomy & histology / Q000821:virology*; D029688:Brassica napus / Q000821:virology; D017796:Caulimovirus / Q000502:physiology*; D005247:Feeding Behavior; D007303:Insect Vectors / Q000502:physiology / Q000821:virology*; D010935:Plant Diseases / Q000821:virology*; D018515:Plant Leaves / Q000821:virology; D017361:Viral Nonstructural Proteins / Q000378:metabolism; D014771:Virion / Q000502:physiology
chemical_list: D017361:Viral Nonstructural Proteins