Ament-Velásquez Sandra Lorena, Tuovinen Veera, Bergström Linnea, Spribille Toby, Vanderpool Dan, Nascimbene Juri, Yamamoto Yoshikazu, Thor Göran, Johannesson Hanna
Department of Organismal Biology, Uppsala University, Uppsala, Sweden.
Department of Ecology, Swedish University of Agricultural Sciences, Uppsala, Sweden.
Front Fungal Biol. 2021 May 26;2:656386. doi: 10.3389/ffunb.2021.656386. eCollection 2021.
The study of the reproductive biology of lichen fungal symbionts has been traditionally challenging due to their complex lifestyles. Against the common belief of haploidy, a recent genomic study found a triploid-like signal in . Here, we infer the genome organization and reproduction in by analyzing genomic data from a pure culture and from thalli, and performing a PCR survey of the MAT locus in natural populations. We found that the read count variation in the four specimens, including the pure culture derived from a single sexual spore of , is consistent with haploidy. By contrast, the read counts from a thallus' metagenome are triploid-like. Characterization of the mating-type locus revealed a conserved heterothallic configuration across the genus, along with auxiliary genes that we identified. We found that the mating-type distributions are balanced in North America for and , suggesting widespread sexual reproduction, but highly skewed in Europe for , consistent with predominant asexuality. Taken together, we propose that fungi are heterothallic and typically haploid, and provide evidence that triploid-like individuals are hybrids between and an unknown lineage, reconciling classic systematic and genetic studies with recent genomic observations.
由于地衣真菌共生体的生活方式复杂，其生殖生物学研究一直具有挑战性。与单倍体的普遍认知相反，最近一项基因组研究在……中发现了类似三倍体的信号。在此，我们通过分析来自纯培养物和叶状体的基因组数据，并对自然种群中的MAT基因座进行PCR调查，来推断……的基因组组织和繁殖情况。我们发现，包括来自……单个有性孢子的纯培养物在内的四个……标本中的读数计数变化与单倍体一致。相比之下，叶状体宏基因组的……读数计数类似三倍体。交配型基因座的特征揭示了该属中保守的异宗配合构型以及我们鉴定出的辅助基因。我们发现，在北美，……和……的交配型分布是平衡的，表明有广泛的有性生殖，但在欧洲，……的交配型分布高度偏斜，这与主要的无性生殖一致。综合来看，我们提出……真菌是异宗配合的且通常是单倍体，并提供证据表明类似三倍体的个体是……与未知……谱系之间的杂交种，从而使经典的系统发育和遗传学研究与最近的基因组观察结果相协调。
