Identification of 23 complementation groups required for post-translational events in the yeast secretory pathway

Coordination of growth with cell division in the yeast Saccharomyces cerevisiae

The fungal vacuole: composition, function, and biogenesis.

https://www.cell.com/cell/pdf/0092-8674(81)90064-7.pdf

Order of events in the yeast secretory pathway

The distribution of actin in wild-type cells and in morphogenetic mutants of the budding yeast Saccharomyces cerevisiae was explored by staining cells with fluorochrome-labeled phallotoxins after fixing and permeabilizing the cells by several methods. The actin appeared to be localized in a set of cortical spots or patches, as well as in a network of cytoplasmic fibers. Bundles of filaments that may possibly correspond to the fibers visualized by fluorescence were observed with the electron microscope. The putative actin spots were concentrated in small and medium-sized buds and at what were apparently the sites of incipient bud formation on unbudded cells, whereas the putative actin fibers were generally oriented along the long axes of the mother-bud pairs. In several morphogenetic mutants that form multiple, abnormally elongated buds, the actin patches were conspicuously clustered at the tips of most buds, and actin fibers were clearly oriented along the long axes of the buds. There was a strong correlation between the occurrence of active growth at particular bud tips and clustering of actin spots at those same tips. Near the end of the cell cycle in wild-type cells, actin appeared to concentrate (as a cluster of spots or a band) in the neck region connecting the mother cell to its bud. Observations made using indirect immunofluorescence with a monoclonal anti-yeast-tubulin antibody on the morphogenetic mutant cdc4 (which forms multiple, abnormally elongated buds while the nuclear cycle is arrested) revealed the surprising occurrence of multiple bundles of cytoplasmic microtubules emanating from the one duplicated spindle-pole body per cell. It seems that most or all of the buds contain one or more of these bundles of microtubules, which often can be seen to extend to the very tips of the buds. These observations are consistent with the hypotheses that actin, tubulin, or both may be involved in the polarization of growth and localization of cell-wall deposition that occurs during the yeast cell cycle.

/pdf/relationship-of-actin-and-tubulin-distribution-to-bud-growth-39ornj58ln.pdf

Relationship of actin and tubulin distribution to bud growth in wild-type and morphogenetic-mutant Saccharomyces cerevisiae.

The interdependence of spindle plaque with other aspects of cell division and conjugation in Saccharomyces cerevisiae has been investigated. Three forms of the spindle plaque appear sequentially before the formation of the complete, intranuclear spindle. The single plaque is present initially in the mitotic cycle; it becomes transformed into a satellite-bearing single plaque during the latter part of G1. Subsequently, plaque duplication yields the double plaque characteristic of the early phase of budding, which coincides with the period of chromosome replication (S). The eventual separation of these plaques to form a complete spindle, with a single plaque at each pole, is nearly coincident with the completion of S. The form of the plaque differs in two independent cases of G1 arrest: the single plaque is found in a cell in stationary arrest of growth, whereas a cell arrested by mating factors in preparation for conjugation contains a satellite-bearing single plaque. The latter form is retained during zygote formation, where it serves as the initial site of fusion of each prezygotic nuceus with the other. This fusion results in the formation of a single zygotic nucleus with a satellite-bearing single plaque, which is subsequently transformed into a double plaque as the zygote buds. The double plaque is situated adjacent to the site of bud emergence in both vegetative cells and zygotes. Images

B Byers

Papers

Behavior of spindles and spindle plaques in the cell cycle and conjugation of Saccharomyces cerevisiae.