Faculty of Education, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan.
Graduate School of Education, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba, 263-8522, Japan.
Mycorrhiza. 2022 Nov;32(5-6):373-385. doi: 10.1007/s00572-022-01086-1. Epub 2022 Jun 29.
Some arbuscular mycorrhizal (AM) fungal species known to form sporocarps (i.e., aggregations of spores) are polyphyletic in two orders, Glomerales and Diversisporales. Spore clusters (sporocarp-like structures) often formed in pot cultures or in vitro conditions are supposed to be clonal populations, while sporocarps in natural habitats with a fungal peridium are morphologically similar to those of epigeous sexual (zygosporic) sporocarps of Endogone species. Thus, in this study, we explored the genetics of sporocarpic spores of two AM fungi with a view to possibilities of clonal or sexual reproduction during sporocarps formation. To examine these possibilities, we investigated single-nucleotide polymorphisms (SNPs) in reduced genomic libraries of spores isolated from sporocarps molecularly identified as Rhizophagus irregularis and Diversispora epigaea. In addition, partial sequences of the MAT locus HD2 gene of R. irregularis were phylogenetically analyzed to determine the nuclear status of the spores. We found that most SNPs were shared among the spores isolated from each sporocarp in both species. Furthermore, all HD2 sequences from spores isolated from three R. irregularis sporocarps were identical. These results indicate that those sporocarps comprise clonal spores. Therefore, sporocarps with clonal spores may have different functions than sexual reproduction, such as massive spore production or spore dispersal via mycophagy.
一些已知形成孢子果（即孢子聚集）的丛枝菌根（AM）真菌在两个目，即球囊霉目和多孢囊霉目是多系的。在盆培或体外条件下形成的孢子簇（类似于孢子果的结构）被认为是克隆种群，而在具有真菌周皮的自然生境中形成的孢子果在形态上与内生性有性（接合）孢子果的 Endogone 物种相似。因此，在这项研究中，我们探索了两种 AM 真菌的孢子果的遗传学，以期在孢子果形成过程中存在克隆或有性繁殖的可能性。为了研究这些可能性，我们调查了从分子鉴定为 Rhizophagus irregularis 和 Diversispora epigaea 的孢子果中分离的孢子的简化基因组文库中的单核苷酸多态性（SNP）。此外，还对 R. irregularis 的 MAT 基因座 HD2 基因的部分序列进行了系统发育分析，以确定孢子的核状态。我们发现，大多数 SNP 在两个物种的每个孢子果中分离的孢子之间是共享的。此外，从三个 R. irregularis 孢子果中分离的孢子的所有 HD2 序列都是相同的。这些结果表明，这些孢子果包含克隆孢子。因此，具有克隆孢子的孢子果可能具有不同于有性繁殖的功能，例如大量孢子产生或通过食菌作用进行孢子散布。
