NUCLEAR TRAFFIC IN FUNGAL HYPHAE - IN-VIVO STUDY OF NUCLEAR MIGRATIONAND POSITIONING IN ASPERGILLUS-NIDULANS

Nuclear migration and nuclear positioning are fundamental processes in all eukaryotic cells. They are easily monitored during hyphal growth of filamentous fungi. We expressed the green fluorescent protein (GFP) as a fusion protein with the putative nuclear localization domain of the transcriptional activator stuA in nuclei of Aspergillus nidulans a nd visualized these organelles in living cells. Nuclear staining was o bserved in interphase nuclei but not during mitosis. Nuclear division, nuclear migration, septum formation and branching were analysed with time-lapse video microscopy during hyphal extension. Hyphae elongated at 0.1-1.2 mu m min(-1) and nuclei moved with similar speeds towards t he hyphal tip until they had reached a defined position. An individual regulation of nuclear mobility in a given hyphal compartment was obse rved. Some representative movies are available on the Internet ww.blac ksci.co.uk/products/journals/molextra.htm). Nuclear positioning was al so studied at the molecular revel. The ApsA protein, which regulates n uclear migration, was localized at the cytoplasmic membrane in germlin gs and hyphae by immunofluorescence and GFP tagging. A model of nuclea r migration, nuclear positioning and the role of ApsA is presented.