title: A Mutation in the Catalytic Subunit of the Glycosylphosphatidylinositol Transamidase Disrupts Growth, Fertility, and Stomata Formation.
abstract: GPI-anchored proteins (GPI-APs) are essential for plant growth and development; knockout mutations in enzymes responsible for anchor biosynthesis or attachment are gametophyte or embryo lethal. In a genetic screen targeted to identify genes regulating stomata formation, we discovered a missense mutation in the Arabidopsis (Arabidopsis thaliana) homolog of GPI8/PIG-K, a Cys protease that transfers an assembled GPI anchor to proteins. The Arabidopsis genome has a single copy of AtGPI8, and the atgpi8-1 mutation reduces the efficiency of this enzyme, leading to reduced accumulation of GPI-anchored proteins. While the atgpi8-1 mutation strongly disrupts plant growth, it is not lethal. Phenotypic analysis of atgpi8-1 mutants suggests that GPI-APs are important for root and shoot growth, stomata formation, apical dominance, transition to flowering, and male gametophyte viability. In addition, atgpi8-1 mutants accumulate higher levels of callose and have reduced plasmodesmata permeability. Genetic interactions of atgpi8-1 with mutations in ERECTA family (ERf) genes suggest the existence of a GPI-AP in a branch of the ERf signaling pathway that regulates stomata formation. Activation of the ERf signal transduction cascade by constitutively active YODA rescues stomata clustering in atgpi8-1, indicating that a GPI-AP functions upstream of the MAP kinase cascade. TOO MANY MOUTHS (TMM) is a receptor-like protein that is able to form heterodimers with ERfs. Our analysis demonstrates that tmm-1 is epistatic to atgpi8-1, indicating that either TMM is a GPI-AP or there is another GPI-AP regulating stomata development whose function is dependent upon TMM.
authors.affiliation: Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996.
authors.forename: Mark G R
authors.identifier: 0000-0002-4463-3382
authors.initials: MG
authors.lastname: Bundy
authors.affiliation: Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996.
authors.forename: Pawel Z
authors.identifier: 0000-0001-5009-4488
authors.initials: PZ
authors.lastname: Kosentka
authors.affiliation: Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996.
authors.forename: Alaina H
authors.identifier: 0000-0002-0163-4772
authors.initials: AH
authors.lastname: Willet
authors.affiliation: Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996.
authors.forename: Liang
authors.identifier: 0000-0002-1395-0465
authors.initials: L
authors.lastname: Zhang
authors.affiliation: Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996.
authors.forename: Emily
authors.identifier: 0000-0001-6956-2253
authors.initials: E
authors.lastname: Miller
authors.affiliation: Department of Biochemistry, Cellular and Molecular Biology, University of Tennessee, Knoxville, Tennessee 37996 shpak@utk.edu.
authors.forename: Elena D
authors.identifier: 0000-0002-5702-7517
authors.initials: ED
authors.lastname: Shpak
mesh_terms: D000595:Amino Acid Sequence; D019881:Aminoacyltransferases / Q000235:genetics / Q000378:metabolism; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D020134:Catalytic Domain; D057056:Cysteine Proteases / Q000235:genetics / Q000378:metabolism*; D005298:Fertility; D005936:Glucans / Q000378:metabolism; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D009154:Mutation; D054046:Plant Stomata / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure; D031425:Plasmodesmata / Q000378:metabolism; D011058:Pollen; D036226:Seedlings / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000648:ultrastructure; D016415:Sequence Alignment; D015398:Signal Transduction
chemical_list: D029681:Arabidopsis Proteins; D005936:Glucans; D017261:Glycosylphosphatidylinositols; C459090:too many mouths protein, Arabidopsis; C048306:callose; D019881:Aminoacyltransferases; C023175:transamidases; D057056:Cysteine Proteases