Department of Biology, University of Ottawa, Ottawa, Ontario, Canada.
Institute of Experimental Botany, The Czech Academy of Science, Prague, Czech Republic.
Environ Microbiol. 2024 Jul;26(7):e16681. doi: 10.1111/1462-2920.16681.
Geosiphon pyriformis, a representative of the fungal sub-phylum Glomeromycotina, is unique in its endosymbiosis with cyanobacteria within a fungal cell. This symbiotic relationship occurs in bladders containing nuclei of G. pyriformis, Mollicutes-like bacterial endosymbionts (MRE), and photosynthetically active and dividing cells of Nostoc punctiforme. Recent genome analyses have shed light on the biology of G. pyriformis, but the genome content and biology of its endosymbionts remain unexplored. To fill this gap, we gathered and examined metagenomic data from the bladders of G. pyriformis, where N. punctiforme and MRE are located. This ensures that our analyses are focused on the organs directly involved in the symbiosis. By comparing this data with the genetic information of related cyanobacteria and MREs from other species of Arbuscular Mycorrhizal Fungi, we aimed to reveal the genetic content of these organisms and understand how they interact at a genetic level to establish a symbiotic relationship. Our analyses uncovered significant gene expansions in the Nostoc endosymbiont, particularly in mobile elements and genes potentially involved in xenobiotic degradation. We also confirmed that the MRE of Glomeromycotina are monophyletic and possess a highly streamlined genome. These genomes show dramatic differences in both structure and content, including the presence of enzymes involved in environmental sensing and stress response.
瓶梗球囊霉是真菌亚门球囊霉目的一个代表，其独特之处在于它与真菌细胞内的蓝细菌共生。这种共生关系发生在含有瓶梗球囊霉核、类似于软壁菌的细菌内共生体（MRE）和具有光合作用活性且正在分裂的念珠藻细胞的泡囊中。最近的基因组分析揭示了瓶梗球囊霉的生物学特性，但它的内共生体的基因组内容和生物学仍未被探索。为了填补这一空白，我们收集并检查了位于瓶梗球囊霉泡囊中的 Nostoc punctiforme 和 MRE 所在位置的宏基因组数据。这确保了我们的分析集中在直接参与共生关系的器官上。通过将这些数据与相关蓝细菌和来自其他丛枝菌根真菌物种的 MRE 的遗传信息进行比较，我们旨在揭示这些生物体的遗传内容，并了解它们在遗传水平上如何相互作用以建立共生关系。我们的分析揭示了 Nostoc 内共生体的显著基因扩张，特别是在移动元件和可能参与异生物质降解的基因中。我们还证实了丛枝菌根真菌的 MRE 是单系的，并且拥有高度精简的基因组。这些基因组在结构和内容上都存在显著差异，包括参与环境感应和应激反应的酶。
