Bakkeren G, Kronstad J W
Biotechnology Laboratory, University of British Columbia, Vancouver, Canada.
Proc Natl Acad Sci U S A. 1994 Jul 19;91(15):7085-9. doi: 10.1073/pnas.91.15.7085.
Sexual compatibility requires self vs. non-self recognition. Genetically, two compatibility or mating-type systems govern recognition in heterothallic basidiomycete fungi such as the edible and woodrotting mushrooms and the economically important rust and smut phytopathogens. A bipolar system is defined by a single genetic locus (MAT) that can have two or multiple alleles. A tetrapolar system has two loci, each with two or more specificities. We have employed two species from the genus Ustilago (smut fungi) to discover a molecular explanation for the genetic difference in mating systems. Ustilago maydis, a tetrapolar species, has two genetically unlinked loci that encode the distinct mating functions of cell fusion (a locus) and subsequent sexual development and pathogenicity (b locus). We have recently described a b locus in a bipolar species, Ustilago hordei, wherein the existence of an a locus has been suspected, but not demonstrated. We report here the cloning of an allele of the a locus (a1) from U. hordei and the discovery that physical linkage of the a and b loci in this bipolar fungus accounts for the distinct mating system. Linkage establishes a large complex MAT locus in U. hordei; this locus appears to be in a region suppressed for recombination.
性兼容性需要自我与非自我识别。从遗传学角度来看，两种兼容性或交配型系统控制着异宗配合担子菌的识别，比如食用蘑菇、木腐菌以及具有重要经济意义的锈菌和黑粉菌等植物病原体。双极性系统由一个单一的基因座（MAT）定义，该基因座可以有两个或多个等位基因。四极性系统有两个基因座，每个基因座有两种或更多种特异性。我们利用黑粉菌属的两个物种来探寻交配系统遗传差异的分子解释。玉米黑粉菌是一种四极性物种，有两个不连锁的基因座，分别编码细胞融合（a基因座）以及随后的有性发育和致病性（b基因座）的不同交配功能。我们最近在一种双极性物种大麦坚黑粉菌中描述了一个b基因座，其中a基因座的存在已被怀疑，但尚未得到证实。我们在此报告从大麦坚黑粉菌中克隆出a基因座的一个等位基因（a1），并发现该双极性真菌中a和b基因座的物理连锁解释了其独特的交配系统。连锁在大麦坚黑粉菌中建立了一个大型复合MAT基因座；该基因座似乎位于一个重组受抑制的区域。
