Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan 48109.
Mycologia. 2013 Nov-Dec;105(6):1374-90. doi: 10.3852/13-162. Epub 2013 Aug 8.
The process of mating in Basidiomycota is regulated by homeodomain-encoding genes (HD) and pheromones and G protein-coupled pheromone receptor genes (P/R). Whether these genes are actually involved in determining mating type distinguishes mating systems that are considered tetrapolar (two locus) from bipolar (one locus). Polyporales are a diverse group of wood-decay basidiomycetes displaying high variability in mating and decay systems. Many of the bipolar species appear to be brown-rot fungi, and it has been hypothesized that there is a functional basis for this correlation. Here we characterize mating genes in recently sequenced Polyporales and other Agaricomycete genomes. All Agaricomycete genomes encode HD and pheromone receptor genes regardless of whether they are bipolar or tetrapolar. The HD genes are organized into a MAT-HD locus with a high degree of gene order conservation among neighboring genes, with the gene encoding mitochondrial intermediate peptidase consistently syntenic but no linkage to the P/R genes. To have a complete dataset of species with known mating systems we determined that Wolfiporia cocos appears to be bipolar, using the criterion that DNA polymorphism of MAT genes should be extreme. Testing the correlation of mating and decay systems while controlling for phylogenetic relatedness failed to identify a statistical association, likely due to the small number of taxa employed. Using a phylogenetic analysis of Ste3 proteins, we identified clades of sequences that contain no known mating type-specific receptors and therefore might have evolved novel functions. The data are consistent with multiple origins of bipolarity within the Agaricomycetes and Polyporales, although the alternative hypothesis that tetrapolarity and bipolarity are reversible states needs better testing.
担子菌门的交配过程受同源域编码基因（HD）和信息素以及 G 蛋白偶联的信息素受体基因（P/R）调控。这些基因是否实际参与决定交配型，将交配系统区分开来，认为是四极（两个位点）还是两极（一个位点）。多孔菌目是一个具有高度多样性的木质腐朽担子菌门，其交配和腐朽系统存在高度的可变性。许多两极物种似乎是褐腐真菌，有人假设这种相关性存在功能基础。在这里，我们描述了最近测序的多孔菌目和其他伞菌目的交配基因和其他 Agaricomycete 基因组。所有 Agaricomycete 基因组都编码 HD 和信息素受体基因，无论它们是两极还是四极。HD 基因组织在 MAT-HD 基因座中，相邻基因之间具有高度的基因顺序保守性，编码线粒体中间肽酶的基因始终是同线性的，但与 P/R 基因没有联系。为了获得具有已知交配系统的物种的完整数据集，我们使用 MAT 基因的 DNA 多态性应该极端的标准，确定 Wolfiporia cocos 似乎是两极的。尽管由于所采用的分类群数量较少，因此未能确定统计关联，但测试交配和腐朽系统之间的相关性而控制系统发育相关性未能确定统计关联。使用 Ste3 蛋白的系统发育分析，我们确定了包含未知交配型特异性受体的序列的进化枝，因此可能已经进化出了新的功能。这些数据与 Agaricomycetes 和多孔菌目内的两极多起源一致，尽管四极和两极是可逆状态的替代假设需要更好的测试。
