title: Subcellular localization and functional analysis of the Arabidopsis GTPase RabE.
abstract: Membrane trafficking plays a fundamental role in eukaryotic cell biology. Of the numerous known or predicted protein components of the plant cell trafficking system, only a relatively small subset have been characterized with respect to their biological roles in plant growth, development, and response to stresses. In this study, we investigated the subcellular localization and function of an Arabidopsis (Arabidopsis thaliana) small GTPase belonging to the RabE family. RabE proteins are phylogenetically related to well-characterized regulators of polarized vesicle transport from the Golgi apparatus to the plasma membrane in animal and yeast cells. The RabE family of GTPases has also been proposed to be a putative host target of AvrPto, an effector protein produced by the plant pathogen Pseudomonas syringae, based on yeast two-hybrid analysis. We generated transgenic Arabidopsis plants that constitutively expressed one of the five RabE proteins (RabE1d) fused to green fluorescent protein (GFP). GFP-RabE1d and endogenous RabE proteins were found to be associated with the Golgi apparatus and the plasma membrane in Arabidopsis leaf cells. RabE down-regulation, due to cosuppression in transgenic plants, resulted in drastically altered leaf morphology and reduced plant size, providing experimental evidence for an important role of RabE GTPases in regulating plant growth. RabE down-regulation did not affect plant susceptibility to pathogenic P. syringae bacteria; conversely, expression of the constitutively active RabE1d-Q74L enhanced plant defenses, conferring resistance to P. syringae infection.
authors.affiliation: Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824, USA.
authors.forename: Elena Bray
authors.initials: EB
authors.lastname: Speth
authors.forename: Lori
authors.initials: L
authors.lastname: Imboden
authors.forename: Paula
authors.initials: P
authors.lastname: Hauck
authors.forename: Sheng Yang
authors.initials: SY
authors.lastname: He
mesh_terms: D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000276:immunology / Q000382:microbiology; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D018506:Gene Expression Regulation, Plant; D006056:Golgi Apparatus / Q000201:enzymology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000378:metabolism; D007113:Immunity, Innate / Q000276:immunology; D020559:Monomeric GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D010935:Plant Diseases / Q000235:genetics / Q000382:microbiology; D018515:Plant Leaves / Q000166:cytology / Q000201:enzymology / Q000235:genetics / Q000382:microbiology; D030821:Plants, Genetically Modified; D011485:Protein Binding; D021381:Protein Transport; D044224:Pseudomonas syringae / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000201:enzymology; D020798:Two-Hybrid System Techniques
chemical_list: D029681:Arabidopsis Proteins; D001426:Bacterial Proteins; D015415:Biomarkers; D050505:Mutant Proteins; D011993:Recombinant Fusion Proteins; C081695:avrPto protein, Pseudomonas syringae; D049452:Green Fluorescent Proteins; D006160:Guanosine Triphosphate; D020559:Monomeric GTP-Binding Proteins