Ultrastructural disorder of the secretory pathway in temperature-sensitive actin mutants of Saccharomyces cerevisiae.
Phenotypes of the two temperature-sensitive actin mutants of Saccharomyces cerevisiae act1-1 and act1-2 at permissive, restrictive and semi-restrictive temperatures were studied by freeze fracture and thin section electron microscopy, and fluorescent microscopy. In contrast to secretory mutants where accumulations of either secretory vesicles, Golgi apparatus, or endoplasmic reticulum were reported, act1-1 and act1-2 mutants revealed accumulation of all the three components, even at permissive temperature. However, more distinct accumulation of secretory organelles was evident during cultivation at the sub-restrictive temperature of 30 degrees C. At the restrictive temperature of 37 degrees C, many cells died, and their empty cell walls remained. Some of the few living cells showed features of apoptosis. From the present study, actin cables are concluded to be necessary for (i) correct spatial positioning and orientation of secretary pathway to the bud and septum, and (ii) vectorial movement of vesicles of the secretory pathway along the actin cables to the bud and septum.
Yamaguchi
Masashi
M
Medical Mycology Research Centre, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8673, Japan. yama@faculty.chiba-u.jp
Kopecká
Marie
M
D000199:Actins / Q000235:genetics*; D005614:Freeze Fracturing; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure; D008854:Microscopy, Electron / Q000379:methods; D008856:Microscopy, Fluorescence / Q000379:methods; D009154:Mutation; D010641:Phenotype; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism; D055571:Secretory Pathway / Q000235:genetics / Q000502:physiology; D013696:Temperature
D000199:Actins; D029701:Saccharomyces cerevisiae Proteins