Department of Ecology and Evolution, Biophore Building, University of Lausanne, 1015, Lausanne, Switzerland.
Vital-IT Group, Swiss Institute of Bioinformatics, 1015, Lausanne, Switzerland.
Mycorrhiza. 2018 May;28(4):369-377. doi: 10.1007/s00572-018-0834-z. Epub 2018 Apr 19.
The genetic state of the arbuscular mycorrhizal fungus species Rhizophagus irregularis differs among isolates, including both homokaryotic and dikaryotic isolates. Via the production of multi-nucleate axexual spores, siblings of dikaryotic isolates may inherit unequal frequencies of nucleotypes. Using bg112, a microsatellite marker, previous studies revealed that lines deriving from single spores of the dikaryotic R. irregularis isolate C3 differed in their proportions of different alleles. A genomic study of single nuclei of R. irregularis, however, suggested that this marker was a multi-copy locus and that therefore it was inappropriate to study the inheritance of nuclei in dikaryotic isolates. In this study, we first analysed whole genome data of several R. irregularis isolates and demonstrated that bg112 is indeed a single copy locus in these genomes. Thus, the bg112 locus is a suitable marker to study the relative frequency of nucleotypes in R. irregularis. Second, by using amplicon sequencing, we confirmed the existence of one allele of bg112 in two homokaryotic isolates (DAOM197198 and C2) and two alleles in the dikaryotic isolate (C3). Finally, we found that the relative proportions of two bg112 alleles differed significantly among dikaryotic single-spore lines derived from isolate C3, indicating that genetically different nucleotypes are inherited unequally in this dikaryotic R. irregularis isolate.
丛枝菌根真菌根内球囊霉种的遗传状态在不同分离株之间存在差异，包括同核和双核分离株。通过产生多核无性孢子，双核分离株的同系物可能会继承不同核型的频率。使用 bg112 微卫星标记，先前的研究表明，来自双核根内球囊霉分离株 C3 的单个孢子衍生的谱系在不同等位基因的比例上存在差异。然而，对单个根内球囊霉细胞核的基因组研究表明，该标记是一个多拷贝基因座，因此不适合研究双核分离株中细胞核的遗传。在这项研究中，我们首先分析了几个根内球囊霉分离株的全基因组数据，证明了 bg112 在这些基因组中确实是一个单拷贝基因座。因此，bg112 基因座是研究根内球囊霉核型相对频率的合适标记。其次，通过使用扩增子测序，我们在两个同核分离株（DAOM197198 和 C2）和一个双核分离株（C3）中证实了 bg112 的一个等位基因的存在，并在双核分离株中发现了两个等位基因。最后，我们发现来自 C3 分离株的双核单孢子系中两个 bg112 等位基因的相对比例存在显著差异，表明在这个双核根内球囊霉分离株中，遗传上不同的核型是不均等地遗传的。
