title: Adjustment of host cells for accommodation of symbiotic bacteria: vacuole defunctionalization, HOPS suppression, and TIP1g retargeting in Medicago.
abstract: In legume-rhizobia symbioses, the bacteria in infected cells are enclosed in a plant membrane, forming organelle-like compartments called symbiosomes. Symbiosomes remain as individual units and avoid fusion with lytic vacuoles of host cells. We observed changes in the vacuole volume of infected cells and thus hypothesized that microsymbionts may cause modifications in vacuole formation or function. To examine this, we quantified the volumes and surface areas of plant cells, vacuoles, and symbiosomes in root nodules of Medicago truncatula and analyzed the expression and localization of VPS11 and VPS39, members of the HOPS vacuole-tethering complex. During the maturation of symbiosomes to become N2-fixing organelles, a developmental switch occurs and changes in vacuole features are induced. For example, we found that expression of VPS11 and VPS39 in infected cells is suppressed and host cell vacuoles contract, permitting the expansion of symbiosomes. Trafficking of tonoplast-targeted proteins in infected symbiotic cells is also altered, as shown by retargeting of the aquaporin TIP1g from the tonoplast membrane to the symbiosome membrane. This retargeting appears to be essential for the maturation of symbiosomes. We propose that these alterations in the function of the vacuole are key events in the adaptation of the plant cell to host intracellular symbiotic bacteria.
authors.affiliation: Laboratory of Molecular Biology, Wageningen University, 6708PB Wageningen, The Netherlands.
authors.forename: Aleksandr
authors.initials: A
authors.lastname: Gavrin
authors.affiliation: School of Agriculture, Food, and Wine, Waite Research Institute, University of Adelaide, Adelaide, South Australia 5064, Australia.
authors.forename: Brent N
authors.initials: BN
authors.lastname: Kaiser
authors.affiliation: Institute for Molecular Plant Physiology and Biophysics, University of Würzburg, D-97082 Würzburg, Germany.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Geiger
authors.affiliation: School of Agriculture, Food, and Wine, Waite Research Institute, University of Adelaide, Adelaide, South Australia 5064, Australia.
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Tyerman
authors.affiliation: School of Agriculture, Food, and Wine, Waite Research Institute, University of Adelaide, Adelaide, South Australia 5064, Australia.
authors.forename: Zhengyu
authors.initials: Z
authors.lastname: Wen
authors.affiliation: Laboratory of Molecular Biology, Wageningen University, 6708PB Wageningen, The Netherlands College of Science, King Saud University, Riyadh 11451, Saudi Arabia.
authors.forename: Ton
authors.initials: T
authors.lastname: Bisseling
authors.affiliation: Laboratory of Molecular Biology, Wageningen University, 6708PB Wageningen, The Netherlands elena.fedorova@wur.nl.
authors.forename: Elena E
authors.initials: EE
authors.lastname: Fedorova
mesh_terms: D000143:Acids / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006863:Hydrogen-Ion Concentration; D046913:Medicago truncatula / Q000166:cytology* / Q000235:genetics / Q000382:microbiology*; D046912:Multiprotein Complexes / Q000378:metabolism*; D009586:Nitrogen Fixation; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D021381:Protein Transport; D034622:RNA Interference; D053204:Root Nodules, Plant / Q000235:genetics / Q000382:microbiology; D013194:Staining and Labeling; D013559:Symbiosis; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D000143:Acids; D015415:Biomarkers; D046912:Multiprotein Complexes; D010940:Plant Proteins