Ime1 and Ime2 are required for pseudohyphal growth of Saccharomyces cerevisiae on nonfermentable carbon sources.
Pseudohyphal growth and meiosis are two differentiation responses to nitrogen starvation of diploid Saccharomyces cerevisiae. Nitrogen starvation in the presence of fermentable carbon sources is thought to induce pseudohyphal growth, whereas nitrogen and sugar starvation induces meiosis. In contrast to the genetic background routinely used to study pseudohyphal growth (Σ1278b), nonfermentable carbon sources stimulate pseudohyphal growth in the efficiently sporulating strain SK1. Pseudohyphal SK1 cells can exit pseudohyphal growth to complete meiosis. Two stimulators of meiosis, Ime1 and Ime2, are required for pseudohyphal growth of SK1 cells in the presence of nonfermentable carbon sources. Epistasis analysis suggests that Ime1 and Ime2 act in the same order in pseudohyphal growth as in meiosis. The different behaviors of strains SK1 and Σ1278b are in part attributable to differences in cyclic AMP (cAMP) signaling. In contrast to Σ1278b cells, hyperactivation of cAMP signaling using constitutively active Ras2(G19V) inhibited pseudohyphal growth in SK1 cells. Our data identify the SK1 genetic background as an alternative genetic background for the study of pseudohyphal growth and suggest an overlap between signaling pathways controlling pseudohyphal growth and meiosis. Based on these findings, we propose to include exit from pseudohyphal growth and entry into meiosis in the life cycle of S. cerevisiae.
Strudwick
Natalie
N
Durham University, School of Biological and Biomedical Sciences, Durham DH1 3LE, United Kingdom.
Brown
Max
M
Parmar
Vipul M
VM
Schröder
Martin
M
D001483:Base Sequence; D002244:Carbon / Q000378:metabolism; D000242:Cyclic AMP / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics; D004843:Epistasis, Genetic; D005285:Fermentation; D005800:Genes, Fungal; D025301:Hyphae / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D008540:Meiosis; D008969:Molecular Sequence Data; D009154:Mutation; D009584:Nitrogen / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D013045:Species Specificity; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
D004271:DNA, Fungal; C080326:IME1 protein, S cerevisiae; D047908:Intracellular Signaling Peptides and Proteins; D009687:Nuclear Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; C089979:UME6 protein, S cerevisiae; D002244:Carbon; D000242:Cyclic AMP; C064979:IME2 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D009584:Nitrogen