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. 2010 Nov 26;30(1):5–16. doi: 10.1038/emboj.2010.299

Figure 6.

Figure 6

The Pex11-Amph region is responsible for Pex11-mediated peroxisome tubulation during organelle fission. (A) Schematic drawing of the yeast fission model used in this study. In dividing H. polymorpha cells lacking the dynamin-related protein Dnm1, actual fission of peroxisomes is blocked. In those cells, an intermediate state in peroxisome proliferation, namely a peroxisomal elongation extending from the mother cell into the bud, is observed. Subsequent deletion of PEX11 in H. polymorpha dnm1 cells disturbs the formation of peroxisomal extensions, but this can be functionally complemented by (P. chrysogenum) PEX11. (B) H. polymorpha dnm1 pex11 cells grown on methanol-containing media usually contain a single, large peroxisome (labelled with DsRed•SKL). Extensions to the bud are not formed. (C) Expression of WT P. chrysogenum PEX11•GFP in H. polymorpha dnm1 pex11 cells restores the formation of peroxisomal extensions. Pex11•GFP is localized on the peroxisomal membrane and accumulates at the basis of the peroxisomal extension marked by DsRed•SKL. Also, PcPex11-Φ•GFP (D) and PcPex11-P•GFP (E) localize to the peroxisome membrane in H. polymorpha dnm1 pex11 cells. However, in these cells, the formation of peroxisomal extensions is not restored. (F–J) The Pex11-Amph is crucial for proliferation of peroxisomes. P. chrysogenum PEX11•GFP and mutants P. chrysogenum PEX11-Φ•GFP or PEX11-P•GFP were introduced into H. polymorpha pex11 cells producing DsRed•SKL to mark peroxisomes. For quantitative analysis of peroxisome numbers, two independent cultures were grown on methanol-containing media and the number of fluorescent spots per cell was counted in 150 cells each. H. polymorpha pex11 cells contain usually a single enlarged peroxisome per cell, but a number of peroxisome-deficient cells can be also observed (average number per cell 0.76; F, G). Expression of P. chrysogenum PEX11•GFP in H. polymorpha pex11 cells causes a significant increase in peroxisome numbers, as multiple organelles can be observed (Student's t-test: P=0.0023; average 1.58) (F, H). Upon expression of either of the mutant genes P. chrysogenum PEX11-Φ•GFP (I) or PEX11-P•GFP (J) in H. polymorpha pex11 cells, the number of organelles was similar to that in the PEX11 deletion strain (averages 0.71 and 0.70, respectively) and significantly different from H. polymorpha pex11 cells producing WT P. chrysogenum PEX11•GFP (Student's t-test: P=0.0015 and 0.0037, respectively). Bars in (F) represent SEM. The bars in B–E and G–J represent 1 μm.