title: Organelle-cytoskeletal interactions: actin mutations inhibit meiosis-dependent mitochondrial rearrangement in the budding yeast Saccharomyces cerevisiae.
abstract: During early stages of meiosis I, yeast mitochondria fuse to form a single continuous thread. Thereafter, portions of the mitochondrial thread are equally distributed to daughter cells. Using time-lapse fluorescence microscopy and a membrane potential sensing dye, mitochondria are resolved as small particles at the cell periphery in pre-meiotic, living yeast. These organelles display low levels of movement. During meiosis I, we observed a threefold increase in mitochondrial motility. Mitochondrial movements were linear, occurred at a maximum velocity of 25 +/- 6.7 nm/s, and resulted in organelle collision and fusion to form elongated tubular structures. Mitochondria do not co-localize with microtubules. Destabilization of microtubules by nocodazole treatment has no significant effect on the rate and extent of thread formation. In contrast, yeast bearing temperature-sensitive mutations in the actin-encoding ACT1 gene (act1-3 and act1-133) exhibit abnormal mitochondrial aggregation, fragmentation, and enlargement as well as loss of mitochondrial motility. In act1-3 cells, mitochondrial defects and actin delocalization occur only at restrictive temperatures. The act1-133 mutation, which perturbs the myosin-binding site of actin without significantly affecting actin cytoskeletal structure in meiotic yeast, results in mitochondrial morphology and motility defects at restrictive and permissive temperatures. These studies support a role for the actin cytoskeleton in the control of mitochondrial position and movements in meiotic yeast.
authors.affiliation: Department of Anatomy and Cell Biology, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA.
authors.forename: M G
authors.initials: MG
authors.lastname: Smith
authors.forename: V R
authors.initials: VR
authors.lastname: Simon
authors.forename: H
authors.initials: H
authors.lastname: O'Sullivan
authors.forename: L A
authors.initials: LA
authors.lastname: Pon
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D003599:Cytoskeleton / Q000378:metabolism*; D008540:Meiosis / Q000502:physiology*; D018715:Microscopy, Video; D008870:Microtubules / Q000187:drug effects / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D009154:Mutation; D009218:Myosins / Q000378:metabolism; D015739:Nocodazole; D012441:Saccharomyces cerevisiae / Q000166:cytology*; D013696:Temperature
chemical_list: D000199:Actins; D009218:Myosins; D015739:Nocodazole