Campbell A M, Rayala H J, Goodenough U W
Department of Biology, Washington University, St. Louis, Missouri 63130-4899, USA.
Mol Biol Cell. 1995 Jan;6(1):87-95. doi: 10.1091/mbc.6.1.87.
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.
异宗配合的莱茵衣藻中的性别分化由两个交配型基因座mt⁺和mt⁻控制，它们表现为一对等位基因，但包含不同的DNA序列。先前已表明，与mt减号连锁的imp11基因突变会将一个减号配子转化为假加号配子，该假加号配子除了表达由mt⁺基因座编码的少数性状外，还表达所有加号配子的性状。在这里，我们描述了iso1突变，该突变与mt⁻基因座不连锁，但仅在减号配子中表达（性别限制表达）。携带iso1突变的减号配子群体表现为减号和假加号配子的混合物：配子同种凝集，但它们不会融合形成合子。进一步分析表明，单个配子表达加号或减号性状：给定的细胞显示一种凝集素（用于性黏附的鞭毛糖蛋白）和一种交配结构。iso1突变鉴定出一个与交配型基因座不连锁的基因，该基因参与性别决定和加号特异性基因的抑制。
