title: Post-Translational Modification and Secretion of Azelaic Acid Induced 1 (AZI1), a Hybrid Proline-Rich Protein from Arabidopsis.
abstract: Arabidopsis EARLI-type hybrid proline-rich proteins (HyPRPs) consist of a putative N-terminal secretion signal, a proline-rich domain (PRD), and a characteristic eight-cysteine-motif (8-CM). They have been implicated in biotic and abiotic stress responses. AZI1 is required for systemic acquired resistance and it has recently been identified as a target of the stress-induced mitogen-activated protein kinase MPK3. AZI1 gel migration properties strongly indicate AZI1 to undergo major post-translational modifications. These occur in a stress-independent manner and are unrelated to phosphorylation by MAPKs. As revealed by transient expression of AZI1 in Nicotiana benthamiana and Tropaeolum majus, the Arabidopsis protein is similarly modified in heterologous plant species. Proline-rich regions, resembling arabinogalactan proteins point to a possible proline hydroxylation and subsequent O-glycosylation of AZI1. Consistently, inhibition of prolyl hydroxylase reduces its apparent protein size. AZI1 secretion was examined using Arabidopsis protoplasts and seedling exudates. Employing Agrobacterium-mediated leaf infiltration of N. benthamiana, we attempted to assess long-distance movement of AZI1. In summary, the data point to AZI1 being a partially secreted protein and a likely new member of the group of hydroxyproline-rich glycoproteins. Its dual location suggests AZI1 to exert both intra- and extracellular functions.
authors.affiliation: Department of Cell Biology, Division of Plant Physiology, University of Salzburg, Hellbrunner Strasse 34, Salzburg A-5020, Austria. Andrea.Pitzschke@sbg.ac.at.
authors.forename: Andrea
authors.initials: A
authors.lastname: Pitzschke
authors.affiliation: Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, Vienna A-1190, Austria. hui.xue@boku.ac.at.
authors.forename: Hui
authors.initials: H
authors.lastname: Xue
authors.affiliation: Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, Vienna A-1190, Austria. Helene.Persak@agrana.com.
authors.forename: Helene
authors.initials: H
authors.lastname: Persak
authors.affiliation: Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, Vienna A-1190, Austria. sneha_datta@yahoo.co.in.
authors.forename: Sneha
authors.initials: S
authors.lastname: Datta
authors.affiliation: Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences, Muthgasse 18, Vienna A-1190, Austria. Georg.Seifert@boku.ac.at.
authors.forename: Georg J
authors.initials: GJ
authors.lastname: Seifert
mesh_terms: D016960:Agrobacterium tumefaciens / Q000235:genetics / Q000378:metabolism; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D006031:Glycosylation; D006909:Hydroxyproline / Q000378:metabolism; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000235:genetics* / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D021381:Protein Transport; D011523:Protoplasts / Q000378:metabolism; D036226:Seedlings / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000235:genetics / Q000378:metabolism; D014162:Transfection
chemical_list: C539888:AZI1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D006909:Hydroxyproline
keywords: AZI1; arabino galactan proteins (AGPs); glycosylation; hybrid proline-rich proteins (HyPRPs); post-translational modification