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The requirement of the LC8 dynein light chain for nuclear migration and septum positioning is temperature dependent in Aspergillus nidulans
Author(s) -
Liu Bo,
Xiang Xin,
Lee YuhRu Julie
Publication year - 2003
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2003.03285.x
Subject(s) - biology , aspergillus nidulans , dynein , mutant , microbiology and biotechnology , hypha , fungal protein , conidiation , microtubule , genetics , gene , botany
Summary In the filamentous fungus Aspergillus nidulans , the multisubunit motor complex cytoplasmic dynein plays essential roles in nuclear migration and septum positioning. The 8 kDa light chain, LC8, the smallest subunit, is conserved among eukaryotic organisms. Besides being a component in the dynein complex, LC8 also interacts with a wide spectrum of mammalian and viral proteins. To date, the function of this small polypeptide is not well understood. To address this issue, we have created a deletion mutation (Δ nudG ) at the nudG locus encoding LC8 in A . nidulans . At 42°C, the Δ nudG mutant forms minute colonies lacking asexual reproduction: this phenotype resembles the phenotype of the dynein heavy chain null mutant. The mutant nuclei largely clustered in the spore body after conidial germination, and the septum was often assembled distally toward the hyphal apex, whereas a control germling has its nuclei distributed along the hypha and the septum formed near the spore body. When the mutant was grown at 23°C, however, its colony resembled a control one, and so did the patterns of nuclear distribution and septum positioning. Elevation of the growth temperature gradually reduced colony size and abolished asexual sporulation. After a period of growth at 23°C that allowed the nuclei to move out of the spore end, a temperature shift to 42°C prevented newly divided nuclei from migrating apart, suggesting that LC8/NUDG was required for both initiating and maintaining dynein motor functions at elevated temperatures. A functional GFP‐NUDA fusion was used to test whether LC8/NUDG is required for DHC (dynein heavy chain)/NUDA localization. We found that at 23°C GFP‐NUDA localized to the hyphal apex and the septation site in Δ nudG cells as in control cells. Such localizations were absent at 42°C in mutant cells, but not in control cells. We conclude that LC8 plays a role in DHC localization/function, and the requirement for such a role in A . nidulans cells is temperature dependent.