title: The Arabidopsis SOS5 locus encodes a putative cell surface adhesion protein and is required for normal cell expansion.
abstract: Cell surface proteoglycans have been implicated in many aspects of plant growth and development, but genetic evidence supporting their function has been lacking. Here, we report that the Salt Overly Sensitive5 (SOS5) gene encodes a putative cell surface adhesion protein and is required for normal cell expansion. The sos5 mutant was isolated in a screen for Arabidopsis salt-hypersensitive mutants. Under salt stress, the root tips of sos5 mutant plants swell and root growth is arrested. The root-swelling phenotype is caused by abnormal expansion of epidermal, cortical, and endodermal cells. The SOS5 gene was isolated through map-based cloning. The predicted SOS5 protein contains an N-terminal signal sequence for plasma membrane localization, two arabinogalactan protein-like domains, two fasciclin-like domains, and a C-terminal glycosylphosphatidylinositol lipid anchor signal sequence. The presence of fasciclin-like domains, which typically are found in animal cell adhesion proteins, suggests a role for SOS5 in cell-to-cell adhesion in plants. The SOS5 protein was present at the outer surface of the plasma membrane. The cell walls are thinner in the sos5 mutant, and those between neighboring epidermal and cortical cells in sos5 roots appear less organized. SOS5 is expressed ubiquitously in all plant organs and tissues, including guard cells in the leaf.
authors.affiliation: Department of Plant Sciences, University of Arizona, Tucson, Arizona 85721, USA.
authors.forename: Huazhong
authors.initials: H
authors.lastname: Shi
authors.forename: YongSig
authors.initials: Y
authors.lastname: Kim
authors.forename: Yan
authors.initials: Y
authors.lastname: Guo
authors.forename: Becky
authors.initials: B
authors.lastname: Stevenson
authors.forename: Jian-Kang
authors.initials: JK
authors.lastname: Zhu
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D015815:Cell Adhesion Molecules / Q000235:genetics* / Q000378:metabolism; D002455:Cell Division / Q000235:genetics / Q000502:physiology; D002473:Cell Wall / Q000235:genetics / Q000502:physiology; D003001:Cloning, Molecular; D005455:Fluorescent Antibody Technique; D018506:Gene Expression Regulation, Plant; D008562:Membrane Glycoproteins / Q000235:genetics* / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D018517:Plant Roots / Q000187:drug effects / Q000254:growth & development; D017386:Sequence Homology, Amino Acid; D012965:Sodium Chloride / Q000494:pharmacology
chemical_list: D029681:Arabidopsis Proteins; D015815:Cell Adhesion Molecules; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; C473610:SOS5 protein, Arabidopsis; D012965:Sodium Chloride