title: CONTINUOUS VASCULAR RING (COV1) is a trans-Golgi network-localized membrane protein required for Golgi morphology and vacuolar protein sorting.
abstract: The trans-Golgi network (TGN) is a tubular-vesicular organelle that matures from the trans cisternae of the Golgi apparatus. In plants, the TGN functions as a central hub for three trafficking pathways: the secretory pathway, the vacuolar trafficking pathway and the endocytic pathway. Here, we describe a novel TGN-localized membrane protein, CONTINUOUS VASCULAR RING (COV1), that is crucial for TGN function in Arabidopsis. The COV1 gene was originally identified from the stem vascular patterning mutant of Arabidopsis thaliana. However, the molecular function of COV1 was not identified. Fluorescently tagged COV1 proteins co-localized with the TGN marker proteins, SYNTAXIN OF PLANTS 4 (SYP4) and vacuolar-type H(+)-ATPase subunit a1 (VHA-a1). Consistently, COV1-localized compartments were sensitive to concanamycin A, a specific inhibitor of VHA. Intriguingly, cov1 mutants exhibited abnormal Golgi morphologies, including a reduction in the number of Golgi cisternae and a reduced association between the TGN and the Golgi apparatus. A deficiency in COV1 also resulted in a defect in vacuolar protein sorting, which was characterized by the abnormal accumulation of storage protein precursors in seeds. Moreover, we found that the development of an idioblast, the myrosin cell, was abnormally increased in cov1 leaves. Our results demonstrate that the novel TGN-localized protein COV1 is required for Golgi morphology, vacuolar trafficking and myrosin cell development.
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University, Kyoto, 606-8502 Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Shirakawa
authors.forename: Haruko
authors.initials: H
authors.lastname: Ueda
authors.forename: Yasuko
authors.initials: Y
authors.lastname: Koumoto
authors.forename: Kentaro
authors.initials: K
authors.lastname: Fuji
authors.forename: Chiaki
authors.initials: C
authors.lastname: Nishiyama
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kohchi
authors.forename: Ikuko
authors.initials: I
authors.lastname: Hara-Nishimura
authors.forename: Tomoo
authors.initials: T
authors.lastname: Shimada
mesh_terms: D029681:Arabidopsis Proteins / Q000378:metabolism*; D002454:Cell Differentiation / Q000187:drug effects; D003208:Concanavalin A / Q000494:pharmacology; D005816:Genetic Complementation Test; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism*; D010641:Phenotype; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism; D058526:Plant Vascular Bundle / Q000187:drug effects / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D055314:Seed Storage Proteins / Q000378:metabolism; D014617:Vacuoles / Q000187:drug effects / Q000378:metabolism*; D021601:trans-Golgi Network / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D000097573:Red Fluorescent Protein
chemical_list: D029681:Arabidopsis Proteins; D003208:Concanavalin A; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D008565:Membrane Proteins; D055314:Seed Storage Proteins; D000097573:Red Fluorescent Protein; C474658:COV1 protein, Arabidopsis
keywords: Arabidopsis thaliana; COV1; Myrosin cell; TGN; Vacuolar protein sorting; Vascular patterning