Laboratory of Genetics, Wageningen University, Wageningen, The Netherlands.
Microbial Ecology Department, NIOO-KNAW, Wageningen, The Netherlands.
Nat Commun. 2021 Feb 4;12(1):783. doi: 10.1038/s41467-021-21050-5.
Some multicellular organisms can fuse because mergers potentially provide mutual benefits. However, experimental evolution in the fungus Neurospora crassa has demonstrated that free fusion of mycelia favours cheater lineages, but the mechanism and evolutionary dynamics of this exploitation are unknown. Here we show, paradoxically, that all convergently evolved cheater lineages have similar fusion deficiencies. These mutants are unable to initiate fusion but retain access to wild-type mycelia that fuse with them. This asymmetry reduces cheater-mutant contributions to somatic substrate-bound hyphal networks, but increases representation of their nuclei in the aerial reproductive hyphae. Cheaters only benefit when relatively rare and likely impose genetic load reminiscent of germline senescence. We show that the consequences of somatic fusion can be unequally distributed among fusion partners, with the passive non-fusing partner profiting more. We discuss how our findings may relate to the extensive variation in fusion frequency of fungi found in nature.
一些多细胞生物可以融合，因为合并可能会提供互惠互利。然而，在真菌粗糙脉孢菌中的实验进化表明，菌丝的自由融合有利于骗子谱系，但这种利用的机制和进化动态尚不清楚。在这里，我们出人意料地表明，所有趋同进化的骗子谱系都有类似的融合缺陷。这些突变体无法启动融合，但仍可以与野生型菌丝融合。这种不对称性降低了骗子-突变体对体细胞基质结合菌丝网络的贡献，但增加了它们核在气生生殖菌丝中的代表。骗子只有在相对较少且可能具有类似于生殖系衰老的遗传负荷时才会受益。我们表明，体细胞融合的后果在融合伙伴之间可能分配不均，被动的非融合伙伴受益更多。我们讨论了我们的发现如何与自然界中发现的真菌融合频率的广泛变化相关。
