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From dikaryon to diploid

机译：从双核体到二倍体

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The dikaryon is the persistent vegetative phase of most basidiomycetes and arises by cell fusion of two haploids carrying different mating type alleles. The diplophase is restricted to a single cell (the basidium) where meiosis takes place. Cell fusion and karyogamy are thus temporally and spatially separated. The dikaryon is characterized by the presence in each cell of two genetically distinct nuclei in a 1:1 ratio and by clamp connections, structures involved in partitioning of the nuclei during their synchronous division. In Coprinopsis cinerea and Schizophyllum commune, with two mating type loci (A and B), heterokaryons with identical A alleles exhibit nuclear migration but no clamps, and those with identical B alleles have unfused clamps (pseudoclamps) and no nuclear migration. Armillaria species are exceptional among basidiomycetes because of their persistent vegetative diploid phase with no clamp connections. Cell fusion is followed immediately by karyogamy. Haploidizadon of the diploid nucleus may occur in the fruiting body, resulting in a new dikaryophase diplophase. Diploids in Ustilago maydis were the first to be synthesized in any basidiomycete. They played a critical role in pioneering studies on DNA recombination and repair. Subsequently diploids were generated in C. cinerea, S. commune, Microbotryum violaceum, and Cryptococcus neoformans. Dikaryons (or heterokaryons) and diploids of the same genotype exhibit phenotypic differences. The reason is not known but evidence indicates that gene expression differs when the same genetic information resides in two nuclei versus one nucleus in the same cell. Diploids in basidiomycete fungi are very stable by themselves but become unstable in 2N + N or 2N + 2N dikaryons. Instability results in haploidization (gradual loss of chromosomes) of the diploid nucleus. The mechanism that triggers this instability is not known. (C) 2015 The British Mycological Society. Published by Elsevier Ltd. All rights reserved.
机译：双核体是大多数担子菌的持续营养期，由携带不同交配型等位基因的两个单倍体的细胞融合产生。双相限于发生减数分裂的单个细胞（钡）。因此，细胞融合和核配子在时间和空间上是分开的。双核体的特征在于每个细胞中以1：1的比例存在两个遗传上不同的核，并具有钳夹连接，参与在其同步分裂过程中分配核的结构。在具有两个交配型基因座（A和B）的灰粉鬼夜蛾和裂褶菌属公社中，具有相同A等位基因的异核体显示出核迁移，但没有钳位，而具有相同B等位基因的杂核体具有未融合的钳位（伪钳位），也没有核迁移。蜜环菌属物种在担子菌中是例外的，因为它们具有持续的营养二倍体相，没有钳位连接。细胞融合后立即发生核型分裂。二倍体核的单倍体可能在子实体中发生，导致新的双核期双倍期。乌斯季亚哥（Estilago maydis）中的二倍体是最早在任何担子菌中合成的。他们在有关DNA重组和修复的开创性研究中发挥了关键作用。随后，在灰葡萄孢菌，葡萄球菌，紫菜和新隐球菌中产生了二倍体。同一基因型的双核（或异核）和二倍体表现出表型差异。原因尚不清楚，但有证据表明，当相同的遗传信息位于同一细胞的两个核与一个核中时，基因表达会不同。担子菌真菌中的二倍体本身非常稳定，但在2N + N或2N + 2N双核生物中变得不稳定。不稳定性导致二倍体核的单倍体化（染色体逐渐丢失）。触发这种不稳定性的机制尚不清楚。 （C）2015英国Mycological Society。由Elsevier Ltd.出版。保留所有权利。

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