Bakkeren G, Kronstad J W
Biotechnology Laboratory, University of British Columbia, Vancouver, Canada.
Plant Cell. 1993 Jan;5(1):123-36. doi: 10.1105/tpc.5.1.123.
In the phytopathogenic fungus Ustilago hordei, one locus with two alternate alleles, MAT-1 and MAT-2, controls mating and the establishment of the infectious dikaryon (bipolar mating). In contrast, for U. maydis, these functions are associated with two different gene complexes, called a and b (tetrapolar mating); the a complex has two alternate specificities, and the b gene complex is multiallelic. We have found homologs for the b gene complex in U. hordei and have cloned one from each mating type using sequences from one bEast allele of U. maydis as a probe. Sequence analysis revealed two divergent open reading frames in each b complex, which we called bW (bWest) and bE (bEast) in analogy with the b gene complex of U. maydis. The predicted bW and bE gene products from the two different mating types showed approximately 75% identity when homologous polypeptides were compared. All of the characterized bW and bE gene products have variable amino-terminal regions, conserved carboxy-terminal regions, and similar homeodomain motifs. Sequence comparisons with the bW1 and bE1 genes of U. maydis showed conservation in organization and structure. Transformation of the U. hordei b gene complex into a U. hordei strain of opposite mating type showed that the b genes from the two mating types are functional alleles. The U. hordei b genes, when introduced into U. maydis, rendered the haploid transformants weakly pathogenic on maize. These results indicate that structurally and functionally conserved b genes are present in U. hordei.
在植物病原真菌大麦坚黑粉菌中，一个具有两个等位基因MAT - 1和MAT - 2的位点控制交配和感染性双核体（双极性交配）的建立。相比之下，对于玉米黑粉菌，这些功能与两个不同的基因复合体相关，称为a和b（四极性交配）；a复合体有两种不同的特异性，b基因复合体是多等位基因的。我们在大麦坚黑粉菌中发现了b基因复合体的同源物，并以玉米黑粉菌一个bEast等位基因的序列为探针，从每种交配型中克隆了一个。序列分析显示每个b复合体中有两个不同的开放阅读框，我们根据玉米黑粉菌的b基因复合体将其分别称为bW（bWest）和bE（bEast）。当比较同源多肽时，来自两种不同交配型的预测bW和bE基因产物显示出约75%的同一性。所有已鉴定的bW和bE基因产物都具有可变的氨基末端区域、保守的羧基末端区域以及相似的同源异型域基序。与玉米黑粉菌的bW1和bE1基因的序列比较显示在组织和结构上具有保守性。将大麦坚黑粉菌的b基因复合体转化到相反交配型的大麦坚黑粉菌菌株中表明，来自两种交配型的b基因是功能等位基因。当将大麦坚黑粉菌的b基因导入玉米黑粉菌时，单倍体转化体对玉米的致病性较弱。这些结果表明大麦坚黑粉菌中存在结构和功能上保守的b基因。
