The iso1 gene of Chlamydomonas is involved in sex determination.
Sexual differentiation in the heterothallic alga Chlamydomonas reinhardtii is controlled by two mating-type loci, mt+ and mt-, which behave as a pair of alleles but contain different DNA sequences. A mutation in the mt minus-linked imp11 gene has been shown previously to convert a minus gamete into a pseudo-plus gamete that expresses all the plus gametic traits except the few encoded by the mt+ locus. Here we describe the iso1 mutation which is unlinked to the mt- locus but is expressed only in minus gametes (sex-limited expression). A population of minus gametes carrying the iso1 mutation behaves as a mixture of minus and pseudo-plus gametes: the gametes isoagglutinate but they do not fuse to form zygotes. Further analysis reveals that individual gametes express either plus or minus traits: a given cell displays one type of agglutinin (flagellar glycoprotein used for sexual adhesion) and one type of mating structure. The iso1 mutation identifies a gene unlinked to the mating-type locus that is involved in sex determination and the repression of plus-specific genes.
Campbell
A M
AM
Department of Biology, Washington University, St. Louis, Missouri 63130-4899, USA.
Rayala
H J
HJ
Goodenough
U W
UW
D000371:Agglutination / Q000187:drug effects; D000373:Agglutinins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001483:Base Sequence; D016825:Chlamydomonas reinhardtii / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development / Q000648:ultrastructure; D003513:Cycloheximide / Q000494:pharmacology; D004229:Dithiothreitol / Q000494:pharmacology; D017343:Genes, Plant; D017125:Genes, Protozoan; D005854:Germ Cells / Q000187:drug effects; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D012732:Sex Determination Analysis; D014415:Tunicamycin / Q000494:pharmacology
D000373:Agglutinins; D010940:Plant Proteins; D014415:Tunicamycin; D003513:Cycloheximide; D004229:Dithiothreitol