The Saccharomyces cerevisiae mutation elm4-1 facilitates pseudohyphal differentiation and interacts with a deficiency in phosphoribosylpyrophosphate synthase activity to cause constitutive pseudohyphal growth.
Saccharomyces cerevisiae mutant E124 was selected in a visual screen based on elongated cell shape. Genetic analysis showed that E124 contains two separate mutations, pps1-1 and elm4-1, each causing a distinct phenotype inherited as a single-gene trait. In rich medium, pps1-1 by itself causes increased doubling time but does not affect cell shape, whereas elm4-1 results in a moderate cell elongation phenotype but does not affect growth rate. Reconstructed elm4-1 pps1-1 double mutants display a synthetic phenotype in rich medium including extreme cell elongation and delayed cell separation, both characteristics of pseudohyphal differentiation. The elm4-1 mutation was shown to act as a dominant factor that potentiates pseudohyphal differentiation in response to general nitrogen starvation in a genetic background in which pseudohyphal growth normally does not occur. Thus, elm4-1 allows recognition of, or response to, a pseudohyphal differentiation signal that results from nitrogen limitation. PPS1 was isolated and shown to be a previously undescribed gene coding for a protein similar in amino acid sequence to phosphoribosylpyrophosphate synthase, a rate-limiting enzyme in the biosynthesis of nucleotides, histidine, and tryptophan. Thus, the pps1-1 mutation may generate a nitrogen limitation signal, which when coupled with elm4-1 results in pseudohyphal growth even in rich medium.
Blacketer
M J
MJ
Department of Biochemistry and Biophysics, Iowa State University, Ames 50011.
Madaule
P
P
Myers
A M
AM
D000595:Amino Acid Sequence; D004271:DNA, Fungal / Q000032:analysis; D017353:Gene Deletion; D005800:Genes, Fungal; D015698:Genomic Library; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010641:Phenotype; D015183:Restriction Mapping; D012268:Ribose-Phosphate Pyrophosphokinase / Q000235:genetics* / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development*; D017386:Sequence Homology, Amino Acid; D013997:Time Factors
D004271:DNA, Fungal; D012268:Ribose-Phosphate Pyrophosphokinase