title: Identification and characterization of LFD-2, a predicted fringe protein required for membrane integrity during cell fusion in neurospora crassa.
abstract: The molecular mechanisms of membrane merger during somatic cell fusion in eukaryotic species are poorly understood. In the filamentous fungus Neurospora crassa, somatic cell fusion occurs between genetically identical germinated asexual spores (germlings) and between hyphae to form the interconnected network characteristic of a filamentous fungal colony. In N. crassa, two proteins have been identified to function at the step of membrane fusion during somatic cell fusion: PRM1 and LFD-1. The absence of either one of these two proteins results in an increase of germling pairs arrested during cell fusion with tightly appressed plasma membranes and an increase in the frequency of cell lysis of adhered germlings. The level of cell lysis in ΔPrm1 or Δlfd-1 germlings is dependent on the extracellular calcium concentration. An available transcriptional profile data set was used to identify genes encoding predicted transmembrane proteins that showed reduced expression levels in germlings cultured in the absence of extracellular calcium. From these analyses, we identified a mutant (lfd-2, for late fusion defect-2) that showed a calcium-dependent cell lysis phenotype. lfd-2 encodes a protein with a Fringe domain and showed endoplasmic reticulum and Golgi membrane localization. The deletion of an additional gene predicted to encode a low-affinity calcium transporter, fig1, also resulted in a strain that showed a calcium-dependent cell lysis phenotype. Genetic analyses showed that LFD-2 and FIG1 likely function in separate pathways to regulate aspects of membrane merger and repair during cell fusion.
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California, USA.
authors.forename: Javier
authors.initials: J
authors.lastname: Palma-Guerrero
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California, USA.
authors.forename: Jiuhai
authors.initials: J
authors.lastname: Zhao
authors.affiliation: IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, Porto, Portugal.
authors.forename: A Pedro
authors.initials: AP
authors.lastname: Gonçalves
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California, USA.
authors.forename: Trevor L
authors.initials: TL
authors.lastname: Starr
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, California, USA Lglass@berkeley.edu.
authors.forename: N Louise
authors.initials: NL
authors.lastname: Glass
mesh_terms: D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D022162:Cytoplasmic Vesicles / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D008561:Membrane Fusion; D009492:Neurospora crassa / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D021381:Protein Transport; D059467:Transcriptome
chemical_list: D005656:Fungal Proteins; D002118:Calcium