title: Identification and characterization of LFD1, a novel protein involved in membrane merger during cell fusion in Neurospora crassa.
abstract: Despite its essential role in development, molecular mechanisms of membrane merger during cell-cell fusion in most eukaryotic organisms remain elusive. In the filamentous fungus Neurospora crassa, cell fusion occurs during asexual spore germination, where genetically identical germlings show chemotropic interactions and cell-cell fusion. Fusion of germlings and hyphae is required for the formation of the interconnected mycelial network characteristic of filamentous fungi. Previously, a multipass membrane protein, PRM1, was characterized and acts at the step of bilayer fusion in N. crassa. Here we describe the identification and characterization of lfd-1, encoding a single pass transmembrane protein, which is also involved in membrane merger. lfd-1 was identified by a targeted analysis of a transcriptional profile of a transcription factor mutant (Δpp-1) defective in germling fusion. The Δlfd-1 mutant shows a similar, but less severe, membrane merger defect as a ΔPrm1 mutant. By genetic analyses, we show that LFD1 and PRM1 act independently, but share a redundant function. The cell fusion frequency of both Δlfd-1 and ΔPrm1 mutants was sensitive to extracellular calcium concentration and was associated with an increase in cell lysis, which was suppressed by a calcium-dependent mechanism involving a homologue to synaptotagmin.
authors.affiliation: Department of Plant and Microbial Biology, University of California, Berkeley, USA.
authors.forename: Javier
authors.initials: J
authors.lastname: Palma-Guerrero
authors.forename: Abigail C
authors.initials: AC
authors.lastname: Leeder
authors.forename: Juliet
authors.initials: J
authors.lastname: Welch
authors.forename: N Louise
authors.initials: NL
authors.lastname: Glass
mesh_terms: D002118:Calcium / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism*; D017353:Gene Deletion; D049770:Genes, Mating Type, Fungal; D008561:Membrane Fusion / Q000235:genetics* / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009492:Neurospora crassa / Q000235:genetics / Q000502:physiology*; D012331:RNA, Fungal / Q000032:analysis; D050857:Synaptotagmins / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics; D059467:Transcriptome
chemical_list: D005656:Fungal Proteins; D008565:Membrane Proteins; D012331:RNA, Fungal; D014157:Transcription Factors; D050857:Synaptotagmins; D002118:Calcium