title: Endoplasmic reticulum subcompartments in a plant parasitic fungus and in baker's yeast: differential distribution of lumenal proteins.
abstract: His-Asp-Glu-Leu (HDEL)-bearing proteins were quantified in different endoplasmic reticulum (ER) subcompartments of Saccharomyces cerevisiae and the plant parasite Uromyces viciae-fabae by immuno-electron microscopy (immuno-EM). In both fungi, the immunogold labeling of these proteins within the ER was three times greater than within the nuclear envelope. In U. viciae-fabae, the ER in germinating uredospores differed from the ER in fungal structures produced within the plant, e.g., haustoria. In haustoria, the cisternal ER differentiated large tubular-vesicular complexes (TVC). TVC contained higher levels of HDEL-bearing proteins than ordinary ER cisternae. ELISA readings also indicated an increased concentration of these proteins in isolated haustoria compared to germinating uredospores. In S. cerevisiae, the ER was differentiated into cortical and internal regions. Immuno-EM revealed that labeling of the binding protein (BiP) was lower in the ER of the cell cortex. Heat shock increased BiP signals, but the relative distribution within the ER did not change. Our results suggest that ER subcompartments can be differentiated by immunogold labeling of proteins with a retention signal. In special cases, such as in the parasitic phase of rust fungi, these proteins accumulate to higher levels in ER subcompartments, probably as a response to plant-induced stress.
authors.affiliation: Universität Konstanz, Fakultät für Biologie, Lehrstuhl für Phytopathologie, Germany.
authors.forename: U
authors.initials: U
authors.lastname: Bachem
authors.forename: K
authors.initials: K
authors.lastname: Mendgen
mesh_terms: D000595:Amino Acid Sequence; D001487:Basidiomycota / Q000737:chemistry / Q000648:ultrastructure*; D015415:Biomarkers; D015153:Blotting, Western; D002352:Carrier Proteins / Q000302:isolation & purification; D002451:Cell Compartmentation; D004721:Endoplasmic Reticulum / Q000737:chemistry / Q000648:ultrastructure*; D004797:Enzyme-Linked Immunosorbent Assay; D007887:Fabaceae / Q000382:microbiology; D005656:Fungal Proteins / Q000276:immunology / Q000302:isolation & purification; D018840:HSP70 Heat-Shock Proteins / Q000276:immunology / Q000302:isolation & purification; D006358:Hot Temperature; D007535:Isomerases / Q000276:immunology / Q000302:isolation & purification; D016253:Microscopy, Immunoelectron; D008969:Molecular Sequence Data; D009685:Nuclear Envelope / Q000648:ultrastructure; D009842:Oligopeptides / Q000276:immunology / Q000302:isolation & purification; D010446:Peptide Fragments / Q000276:immunology; D010946:Plants, Medicinal; D019704:Protein Disulfide-Isomerases; D021382:Protein Sorting Signals; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000648:ultrastructure*; D014018:Tissue Distribution
chemical_list: D015415:Biomarkers; D002352:Carrier Proteins; D005656:Fungal Proteins; D018840:HSP70 Heat-Shock Proteins; C060153:KAR2 protein, yeast; D009842:Oligopeptides; D010446:Peptide Fragments; D021382:Protein Sorting Signals; C077480:histidyl-aspartyl-glutamyl-leucine; D007535:Isomerases; D019704:Protein Disulfide-Isomerases