Pattern of end growth of the fission yeast Schizosaccharomyces pombe

The patterns of end growth of individual cells of Schizosaccharomyces pombe, wild-type cells (strain 972 h−), cells exposed to 8 mM hydroxyurea, and cdc mutants (cdc11-123 and cdc2-33), were investigated by time-lapse photomicrography. It was reconfirmed that there are three patterns of end growth: cells growing at the old end, at the new end, and at both ends from the beginning of the cell cycle. Cells that initiated growth at the old (new) end increased their growth rate at the new (old) end and became constant in their growth rate at the old (new) end when cells had their growth rate higher than a critical value: 0.08, 0.09, 0.08, and 0.11 μm/min in wild-type cells, cells exposed to hydroxyurea, cdc11-123 cells, and cdc2-33 cells, respectively. The critical value is proportional to the doubling time in length. Key words: extension, growth, fission yeast.

Patterns of extension growth of the fission yeast, Schizosaccharomyces pombe

The growth of sausage-shaped cells of the fission yeast, Schizosaccharomyces pombe (strain NCYC 132), was followed in the second or third cycle by time-lapse photomicrography. Experimental cells were harvested from glucose-limited (0.2% glucose EMM3) chemostat culture (dilution rate, 0.125/h) and were plated onto a slide with EMM3 agar (2% glucose). By observing their extension patterns, we found some rules of extension growth. Thus, (1) all sibs with walls newly formed in the previous cycle, whose progenitor cells grew at the old end (followed Mitchison's rule), grow at the old end (also follow Mitchison's rule). (2) Sibs with old walls whose progenitor cell followed Mitchison's rule behave in one of three ways: (i) growth at the old end (follow Mitchison's rule); (ii) growth at the new end (violate Mitchison's rule); or (iii) growth at both ends (bipolar). (3) Both sibs whose progenitor grew at both ends (bipolar) always grow at the old end (follow Mitchison's rule).

Control of cell size and cycle time in Schizosaccharomyces pombe

Steady-state and perturbed cells of Schizosaccharomyces pombe have been observed through several division cycles by time-lapse photomicrography. Perturbed cells were produced by the use of a conditional cell division cycle mutant in which nuclear division is reversibly blocked at high temperature. These experiments show that in both populations cell length at division and cell cycle duration are homeostatically controlled, probably by a primary size-control mechanism. Cycle time is indirectly controlled, as cells which have an extended cycle are on average larger at division, so that duaghters of such cells need to grow by a smaller amount and for a shorter period, before dividing again. In general, deviations from the mean are corrected within a single cycle, but in the case of very long cells the control breaks down because the cycle cannot be shortened by more than a quarter under the conditions used. These cells take more than one cycle to return to normal.

Light and electron microscopic observations of conidiogenesis in Peziza quelepidotia

Conidium ontogeny of the botryose solitary blastospores of Peziza quelepidotia Korf and O'Donnell was followed by time-lapse photomicrography using differential interference-contrast illumination in an inexpensive, commercially available, slide culture chamber. This chamber has several advantages over those previously described. Subsequent to time-lapse photomicrography, techniques are described for viewing these identical conidiophores in all stages of development in the scanning electron microscope. Transmission electron microscopic observations were conducted to fully characterize conidiogenesis and to unequivocally determine its location in hyphomycete classification schemes. This imperfect state, which belongs to Hughes' conidiogenetic section 1B, bears determinate retrogressive conidiogenous cells and single holoblastic conidia with multiple synchronous conidiogenous loci. However, unlike other members of the Botryoblastosporae, the conidia are not borne on well differentiated swollen conidiogenous cells (i.e., ampullae). Ultrastructural observations were made on the spatial relationship between the conidial state and ascogonia and on germinating conidia.

Conidium ontogeny in hyphomycetes. The meristem arthrospores of Wallemia sebi

Conidium ontogeny in Wallemia sebi (Fr.) v. Arx is analyzed and illustrated by time-lapse photomicrography. The nuclear configurations occurring during conidiogenesis are described and subsequent nuclear distribution reported. The conidia are considered to be meristem arthrospores of a unique type.

Conidium ontogeny in hyphomycetes. The blastoconidia of Cladosporium herbarum and Torula herbarum

Conidium ontogeny in Cladosporium herbarum (Pers.) Link ex S. F. Gray and Torula herbarum (Pers.) Link ex S. F. Gray is analyzed by time-lapse photomicrography. Both fungi are shown to produce conidia holoblastically in acropetal chains.