Peroxisome dynamics and morphogenesis in wild-type and pex3BΔ cells visualized by 4D in vivo video microscopy. Peroxisomes were fluorescently labeled with genomically encoded Pot1p-GFP. Cells were grown for 16 h in YPD, transferred to YPBO for 6 h, and visualized at 28°C (A and B) or 23°C (C) with an LSM 510 confocal microscope specifically modified for 4D in vivo microscopy (see Materials and methods). (A) Wild-type E122/POT1-GFP strain. Representative frames from Video 1 show the specific movements and division of peroxisomes through several cell divisions. The emergence of new buds at 1 h 1 min, 1 h 22 min, and 2 h 45 min is followed by the vectorial transfer of a portion of the mother cell's peroxisomes to the bud, where they associate with the bud tip. Bar, 5 µm. (B and C) pex3BΔ/POT1-GFP strain. (B) Representative frames from Video 2 display the specific movements and morphogenesis of peroxisomes in pex3B cells. At 0 min, both buds lack peroxisomes. By 12 min, several peroxisomes have entered the buds but have failed to associate with the bud tips. Subsequently, many peroxisomes undergo a morphogenic transition, becoming elongated and tubular-reticular in appearance. These peroxisomes often straddle the mother-bud neck (2 h 26 min). Also, peroxisome inheritance does not keep pace with cell division, as many buds are devoid of peroxisomes at later time points (4 h 5 min). Bar, 5 µm. (C) Representative frames from Video 3 display the inability of a tubular-reticular peroxisome to divide except through cytokinesis. A tubular reticular peroxisome is seen initially straddling the mother-bud neck (0 min). At 1 h 48 min, the peroxisome is cut in two by constriction of the septin ring, concluding cytokinesis. A second scission event occurs at 3 h with the conclusion of cytokinesis between the mother cell and the bud to her right. Subsequent buds fail to inherit peroxisomes (4 h 49 min). Bar, 5 µm.