title: VAMP721a and VAMP721d are important for pectin dynamics and release of bacteria in soybean nodules.
abstract: In root nodules rhizobia enter host cells via infection threads. The release of bacteria to a host cell is possible from cell wall-free regions of the infection thread. We hypothesized that the VAMP721d and VAMP721e exocytotic pathway, identified before in Medicago truncatula, has a role in the local modification of cell wall during the release of rhizobia. To clarify the role of VAMP721d and VAMP721e we used Glycine max, a plant with a determinate type of nodule. The localization of the main polysaccharide compounds of primary cell walls was analysed in control vs nodules with partially silenced GmVAMP721d. The silencing of GmVAMP721d blocked the release of rhizobia. Instead of rhizobia-containing membrane compartments - symbiosomes - the infected cells contained big clusters of bacteria embedded in a matrix of methyl-esterified and de-methyl-esterified pectin. These clusters were surrounded by a membrane. We found that GmVAMP721d-positive vesicles were not transporting methyl-esterified pectin. We hypothesized that they may deliver the enzymes involved in pectin turnover. Subsequently, we found that GmVAMP721d is partly co-localized with pectate lyase. Therefore, the biological role of VAMP721d may be explained by its action in delivering pectin-modifying enzymes to the site of release.
authors.affiliation: Laboratory of Molecular Biology, Department of Plant Sciences, Graduate School Experimental Plant Sciences, Wageningen University, 6708 PB, Wageningen, the Netherlands.
authors.forename: Aleksandr
authors.initials: A
authors.lastname: Gavrin
authors.affiliation: School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA, 5050, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Chiasson
authors.affiliation: School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA, 5050, Australia.
authors.forename: Evgenia
authors.initials: E
authors.lastname: Ovchinnikova
authors.affiliation: School of Agriculture Food and Wine, The University of Adelaide, Adelaide, SA, 5050, Australia.
authors.forename: Brent N
authors.initials: BN
authors.lastname: Kaiser
authors.affiliation: Laboratory of Molecular Biology, Department of Plant Sciences, Graduate School Experimental Plant Sciences, Wageningen University, 6708 PB, Wageningen, the Netherlands.
authors.forename: Ton
authors.initials: T
authors.lastname: Bisseling
authors.affiliation: Laboratory of Molecular Biology, Department of Plant Sciences, Graduate School Experimental Plant Sciences, Wageningen University, 6708 PB, Wageningen, the Netherlands.
authors.forename: Elena E
authors.initials: EE
authors.lastname: Fedorova
mesh_terms: D002482:Cellulose / Q000378:metabolism; D004951:Esterification; D020868:Gene Silencing; D010368:Pectins / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism*; D011133:Polysaccharide-Lyases / Q000378:metabolism; D021381:Protein Transport; D012231:Rhizobium / Q000502:physiology*; D053204:Root Nodules, Plant / Q000378:metabolism / Q000382:microbiology* / Q000648:ultrastructure; D013025:Glycine max / Q000378:metabolism* / Q000382:microbiology*; D013559:Symbiosis
chemical_list: D010940:Plant Proteins; D010368:Pectins; D002482:Cellulose; D011133:Polysaccharide-Lyases; C023911:pectate lyase
keywords: endosymbiosis; exocytosis; intracellular infection; legume-rhizobia symbiosis; plant cell wall; soybean