title: EXO70A1-mediated vesicle trafficking is critical for tracheary element development in Arabidopsis.
abstract: Exocysts are highly conserved octameric complexes that play an essential role in the tethering of Golgi-derived vesicles to target membranes in eukaryotic organisms. Genes encoding the EXO70 subunit are highly duplicated in plants. Based on expression analyses, we proposed previously that individual EXO70 members may provide the exocyst with functional specificity to regulate cell type- or cargo-specific exocytosis, although direct evidence is not available. Here, we show that, as a gene expressed primarily during tracheary element (TE) development, EXO70A1 regulates vesicle trafficking in TE differentiation in Arabidopsis thaliana. Mutations of EXO70A1 led to aberrant xylem development, producing dwarfed and nearly sterile plants with very low fertility, reduced cell expansion, and decreased water potential and hydraulic transport. Grafting of a mutant shoot onto wild-type rootstock rescued most of these aboveground phenotypes, while grafting of a wild-type shoot to the mutant rootstock did not rescue the short root hair phenotype, consistent with the role of TEs in hydraulic transport from roots to shoots. Histological analyses revealed an altered pattern of secondary cell wall thickening and accumulation of large membrane-bound compartments specifically in developing TEs of the mutant. We thus propose that EXO70A1 functions in vesicle trafficking in TEs to regulate patterned secondary cell wall thickening.
authors.affiliation: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing, 100093, China.
authors.forename: Shipeng
authors.initials: S
authors.lastname: Li
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.forename: Dali
authors.initials: D
authors.lastname: Yu
authors.forename: Shichao
authors.initials: S
authors.lastname: Ren
authors.forename: Shufeng
authors.initials: S
authors.lastname: Sun
authors.forename: Linde
authors.initials: L
authors.lastname: Liu
authors.forename: Tijs
authors.initials: T
authors.lastname: Ketelaar
authors.forename: Anne-Mie C
authors.initials: AM
authors.lastname: Emons
authors.forename: Chun-Ming
authors.initials: CM
authors.lastname: Liu
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D049109:Cell Proliferation; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism / Q000648:ultrastructure; D005089:Exocytosis / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D017403:In Situ Hybridization; D018613:Microscopy, Confocal; D046529:Microscopy, Electron, Transmission; D009154:Mutation; D051479:Plant Infertility / Q000235:genetics; D018517:Plant Roots / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D018520:Plant Shoots / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D018547:Plant Stems / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D054817:Pollination / Q000235:genetics; D022161:Transport Vesicles / Q000378:metabolism*; D033921:Vesicular Transport Proteins / Q000235:genetics / Q000378:metabolism; D014867:Water / Q000378:metabolism; D052584:Xylem / Q000166:cytology / Q000235:genetics / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C515561:EXO70A1 protein, Arabidopsis; D033921:Vesicular Transport Proteins; D014867:Water