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Schizosaccharomyces pombe mutants affected in their division response to starvation
1Department of Biology, Queen's University, Kingston, Ontario, Canada.
Abstract:
Schizosaccharomyces pombe mutants have been selected on the basis of an altered response to nutritional stimulation of cell division (changed division response, cdr). Two new loci (cdr1 and cdr2) were identified and characterized. When suspended in nitrogen-free medium wild-type cells underwent stimulated rates of division and became reduced to approximately 30% in protein content with a concomitant 3.6-fold increase in cell number after 24 h starvation. cdr cells had significantly smaller increases in cell number. The ratio of starved/unstarved protein content was higher for the cdr strains than for the wild type. cdr cells were also affected in their response to nitrogen-source shifts from proline to glutamate (or vice versa) or when shifted from serine phosphate to inorganic phosphate, showing that the alteration in division response was not restricted to nitrogen metabolism. Upon nitrogen starvation wild-type cells arrested prior to the cdc10 execution point, whereas cdr cells arrested later in the cell cycle. cdc25-22 cdr1 or cdr2 double mutants grew very slowly and were extremely elongated at all temperatures; the restrictive temperature was reduced to 27 degrees C. wee1 was epistatic to cdr mutations with respect to cell length at the cell plate stage. cdr+ genes are postulated to play a role in the nutritional modulation of the mitotic size control.
Insights
New Schizosaccharomyces pombe mutants, cdr1 and cdr2, show altered responses to nutritional cues affecting cell division. These findings suggest cdr genes are crucial for modulating cell division based on nutrient availability.
Area of Science:
- * Molecular and Cellular Biology
- * Yeast Genetics
- * Cell Cycle Regulation
Background:
- * Nutritional stimuli significantly impact cell division rates and protein content in wild-type Schizosaccharomyces pombe.
- * Previous studies indicated that nutrient availability influences cell cycle progression, but specific genetic factors remain to be fully elucidated.
Purpose of the Study:
- * To identify and characterize novel genetic loci involved in the nutritional regulation of cell division in Schizosaccharomyces pombe.
- * To investigate the role of these genes in cell cycle progression and size control under various nutritional conditions.
Main Methods:
- * Selection of Schizosaccharomyces pombe mutants with altered responses to nutritional stimulation of cell division (changed division response, cdr).
- * Characterization of two new loci, cdr1 and cdr2, through genetic analysis and phenotypic observation under nutrient starvation and shifts.
- * Analysis of cell cycle arrest points and interactions with known cell cycle genes (cdc10, cdc25, wee1).
Main Results:
- * Mutants cdr1 and cdr2 exhibited significantly reduced cell number increases under nitrogen starvation compared to wild-type cells.
- * cdr mutants showed altered responses to various nutrient shifts, indicating a broader role beyond nitrogen metabolism.
- * Nitrogen starvation led to later cell cycle arrest in cdr mutants compared to wild-type cells.
- * Double mutants (cdc25-22 cdr1/cdr2) displayed slow growth, extreme elongation, and a reduced restrictive temperature, with wee1 being epistatic to cdr mutations regarding cell length.
Conclusions:
- * The identified cdr1 and cdr2 genes are essential for the proper nutritional modulation of cell division in Schizosaccharomyces pombe.
- * These genes play a critical role in linking nutrient availability to the mitotic size control mechanisms.
- * Further research into cdr genes can provide deeper insights into the complex interplay between nutrition and cell cycle regulation.
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