Exogenous inositol and genes responsible for inositol transport are required for mating and sporulation in Shizosaccharomyces pombe.
Fission yeast, Schizosaccharomyces pombe, is a natural inositol auxotroph. We show here that the amount of exogenous inositol added to the medium is critical for the control of its life cycle. Above growth-limiting concentrations inositol stimulates mating and sporulation in minimal medium. The effect of inositol is also observed on yeast-extract-medium plates. We selected a mutant, IM49, which mates and sporulates only poorly and show that it is defective in inositol transport. Its defect is in a gene (itr2) coding for a putative 12 membrane-spanning protein. The polypeptide contains the two sugar-transport motifs typical for hexose transporters and shows good homology to the two Saccharomyces cerevisiae inositol transporters. The itr2 gene is essential for cell growth and its mRNA level is repressed by glucose. Mutant IM49 is also complemented by a multicopy suppressor gene (itr1) which codes for a putative hexose transporter with unknown substrate specifity.
Niederberger
C
C
Institute of General Microbiology, University of Bern, Switzerland.
Gräub
R
R
Schweingruber
A M
AM
Fankhauser
H
H
Rusu
M
M
Poitelea
M
M
Edenharter
L
L
Schweingruber
M E
ME
D000595:Amino Acid Sequence; D001483:Base Sequence; D001693:Biological Transport, Active / Q000235:genetics; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017931:DNA Primers / Q000235:genetics; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005800:Genes, Fungal; D005816:Genetic Complementation Test; D007294:Inositol / Q000378:metabolism*; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D009004:Monosaccharide Transport Proteins; D009154:Mutation; D010641:Phenotype; D015183:Restriction Mapping; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D012568:Schizosaccharomyces / Q000235:genetics* / Q000254:growth & development / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013172:Spores, Fungal / Q000235:genetics / Q000502:physiology
D002352:Carrier Proteins; D017931:DNA Primers; D005656:Fungal Proteins; C069143:ITR1 protein, S cerevisiae; C069144:ITR2 protein, S cerevisiae; D026901:Membrane Transport Proteins; D009004:Monosaccharide Transport Proteins; D029701:Saccharomyces cerevisiae Proteins; D007294:Inositol