title: The monomeric GTPase RabA2 is required for progression and maintenance of membrane integrity of infection threads during root nodule symbiosis.
abstract: Progression of the infection canal that conducts rhizobia to the nodule primordium requires a functional Rab GTPase located in Golgi/trans-Golgi that also participate in root hair polar growth. Common bean (Phaseolus vulgaris) symbiotically associates with its partner Rhizobium etli, resulting in the formation of root nitrogen-fixing nodules. Compatible bacteria can reach cortical cells in a tightly regulated infection process, in which the specific recognition of signal molecules is a key step to select the symbiotic partner. In this work, we show that RabA2, a monomeric GTPase from common bean, is required for the progression of the infection canal, referred to as the infection thread (IT), toward the cortical cells. Expression of miss-regulated mutant variants of RabA2 resulted in an increased number of abortive infection events, including bursting of ITs and a reduction in the number of nodules. Nodules formed in these plants were small and contained infected cells with disrupted symbiosome membranes, indicating either early senescence of these cells or defects in the formation of the symbiosome membrane during bacterial release. RabA2 localized to mobile vesicles around the IT, but mutations that affect GTP hydrolysis or GTP/GDP exchange modified this localization. Colocalization of RabA2 with ArfA1 and a Golgi marker indicates that RabA2 localizes in Golgi stacks and the trans-Golgi network. Our results suggest that RabA2 is part of the vesicle transport events required to maintain the integrity of the membrane during IT progression.
authors.affiliation: Instituto de Biotecnología y Biología Molecular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Centro Científico y Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, calle 115 y 49 s/n, CP 1900, La Plata, Argentina.
authors.forename: Virginia
authors.initials: V
authors.lastname: Dalla Via
authors.affiliation: Instituto de Biotecnología y Biología Molecular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Centro Científico y Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, calle 115 y 49 s/n, CP 1900, La Plata, Argentina.
authors.forename: Soledad
authors.initials: S
authors.lastname: Traubenik
authors.affiliation: Instituto de Biotecnología y Biología Molecular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Centro Científico y Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, calle 115 y 49 s/n, CP 1900, La Plata, Argentina.
authors.forename: Claudio
authors.initials: C
authors.lastname: Rivero
authors.affiliation: Instituto de Biotecnología y Biología Molecular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Centro Científico y Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, calle 115 y 49 s/n, CP 1900, La Plata, Argentina.
authors.forename: O Mario
authors.initials: OM
authors.lastname: Aguilar
authors.affiliation: Instituto de Biotecnología y Biología Molecular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Centro Científico y Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, calle 115 y 49 s/n, CP 1900, La Plata, Argentina.
authors.forename: María Eugenia
authors.identifier: http://orcid.org/0000-0001-9565-1743
authors.initials: ME
authors.lastname: Zanetti
authors.affiliation: Instituto de Biotecnología y Biología Molecular, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Centro Científico y Tecnológico-La Plata, Consejo Nacional de Investigaciones Científicas y Técnicas, calle 115 y 49 s/n, CP 1900, La Plata, Argentina. fablanco@biol.unlp.edu.ar.
authors.forename: Flavio Antonio
authors.identifier: http://orcid.org/0000-0002-8380-8472
authors.initials: FA
authors.lastname: Blanco
mesh_terms: D002462:Cell Membrane / Q000382:microbiology; D018506:Gene Expression Regulation, Plant; D006056:Golgi Apparatus / Q000378:metabolism; D009154:Mutation; D027805:Phaseolus / Q000382:microbiology / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018517:Plant Roots / Q000235:genetics / Q000382:microbiology; D030821:Plants, Genetically Modified; D012231:Rhizobium / Q000502:physiology*; D053204:Root Nodules, Plant / Q000235:genetics / Q000382:microbiology*; D013559:Symbiosis; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D010940:Plant Proteins; D020691:rab GTP-Binding Proteins
keywords: Legume; Nitrogen fixation; Nodulation; Rhizobia; Vesicle transport