title: The Hematopoietic Organ: A Cornerstone for Wolbachia Propagation Between and Within Hosts.
abstract: Wolbachia is an intracellular α-proteobacterium which is transmitted vertically from mother to offspring but also frequently switches horizontally from one host to another. Our hypothesis is based on the role of immune cells and the organs that produce them, the hematopoietic organs (HOs), as primordial niches for the propagation of Wolbachia via hemocytes both (i) within hosts: to initiate and maintain the systemic infection and (ii) between hosts: to promote both vertical and horizontal transmission of Wolbachia. Therefore, we review some fundamental ideas underlying this hypothesis and go further with new empirical data that lead to a first close-up analysis of the potential role of HOs in Wolbachia propagation. The monitoring of the first steps of Wolbachia infection in horizontally infected host organs by transmission electron microscopy and qPCR suggests that (i) HOs are colonized early and extensively as soon as they are in contact with Wolbachia which find in these cells a favorable niche to multiply and (ii) infected HOs which expel hemocytes all lifelong can generate and maintain a systemic infection that could contribute to increase both vertical and horizontal propagation of these symbionts.
authors.affiliation: CNRS UMR 7267, Laboratoire Ecologie et Biologie des Interactions, Université de Poitiers Poitiers, France.
authors.forename: Christine
authors.initials: C
authors.lastname: Braquart-Varnier
authors.affiliation: CNRS UMR 7267, Laboratoire Ecologie et Biologie des Interactions, Université de Poitiers Poitiers, France.
authors.forename: Maryline
authors.initials: M
authors.lastname: Raimond
authors.affiliation: CNRS UMR 7267, Laboratoire Ecologie et Biologie des Interactions, Université de Poitiers Poitiers, France.
authors.forename: Gaëtan
authors.initials: G
authors.lastname: Mappa
authors.affiliation: Genetics Department, Texas Biomedical Research Institute, San Antonio TX, USA.
authors.forename: Frédéric D
authors.initials: FD
authors.lastname: Chevalier
authors.affiliation: Genetics Department, Texas Biomedical Research Institute, San Antonio TX, USA.
authors.forename: Winka
authors.initials: W
authors.lastname: Le Clec'h
authors.affiliation: Institut des Sciences de l'Evolution de Montpellier (UMR CNRS-IRD-UM 5554), Université de Montpellier Montpellier, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Sicard
keywords: Wolbachia; hematopoietic organs; hemocytes; intracellular endosymbiont; mobile vector; symbiosis; terrestrial isopod