Dynamic distribution of BIMG^PP1 in living hyphae of Aspergillus indicates a novel role in septum formation

Abstract

SummaryMutation of bim G, the major protein phosphatase 1 gene in Aspergillus nidulans , causes multiple cell cycle and hyphal growth defects that are associated with overphosphorylation of subcellular components. We have used functional translational fusions with the green fluorescent protein (GFP) to show that BIMG has at least four discrete locations within growing hyphae. Three of these locations, the hyphal tip, the spindle pole body and the nucleus, correlate with previously known requirements for bim G PP1 in mitosis and hyphal growth and are highly dynamic. BIMG-GFP in the hyphal tip seemed to be associated with the plasma membrane and formed a collar of fluorescence within the apical dome. The distribution of nuclear BIMG-GFP varied depending on nutritional conditions; on poor medium, it concentrated more in the nucleolus than in the nucleoplasm, whereas on rich medium, it was more evenly distributed between the two nuclear regions. The association of BIMG-GFP with developing septa was transient, and we present evidence that BIMG phosphatase plays a direct role in septum formation, distinct from its role in mitosis. We conclude that, by being physically present at several sites, the BIMG phosphatase has roles in multiple cellular processes.

Schizosaccharomyces pombeprotein phosphatase 1 in mitosis, endocytosis and a partnership with Wsh3/Tea4 to control polarised growth

“…Thus, like its A. nidulans homologue BimG, Dis2 function is required for tip growth (Doonan and Morris, 1989;Fox et al, 2002). The requirement for PP1 function during recovery from stress, echoes the requirement for phosphorylation of the polo kinase Plo1 on serine 402 to promote tip growth during recovery from centrifugation and heat stress (Petersen and Hagan, 2005).…”

“…As in S. pombe, discrete Glc7 spots co-localise with proteins associated with centromeres at the apex of anaphase nuclei (Bloecher and Tatchell, 2000). A discrete BimG dot mirrors the behaviour of centromeric Dis2 in associating with the SPB region throughout the cell cycle with the exception of the period when centromeres leave the SPB from mitotic entry until anaphase (Fox et al, 2002;Funabiki et al, 1993). However, it remains to be established whether this distribution arises from the association of PP1 with centromeres.…”

“…The single PP1 isoforms of A. nidulans and S. cerevisiae, BimG and Glc7, respectively, also accumulate in nuclei. Glc7 is permanently enriched in the nucleolus whereas BimG is a general nuclear protein in rich conditions, but accumulates in nucleoli during growth on a poor carbon source (Bloecher and Tatchell, 2000;Fox et al, 2002). As in S. pombe, discrete Glc7 spots co-localise with proteins associated with centromeres at the apex of anaphase nuclei (Bloecher and Tatchell, 2000).…”

“…Both Glc7 and BimG accumulate around the cytokinetic ring, the tips of growing hyphae or buds and sites from which hyphae will branch, or buds will emerge, respectively (Bloecher and Tatchell, 2000;Fox et al, 2002). Cortical PP1 has been studied in greatest detail in budding yeast, but it is clear that BimG is required for polarised growth during sporulation and vegetative growth (Doonan and Morris, 1989b;Fox et al, 2002).…”

Disruption of theAspergillus fumigatusGene Encoding Nucleolar Protein CgrA Impairs Thermotolerant Growth and Reduces Virulence

“…5E and F). The nucleolus occupies a substantial proportion of the nuclear volume due to the high on May 10, 2018 by guest http://iai.asm.org/ demand for ribosomes in an organism that has a relatively small genome (23,68). The strain shown in Fig.…”