Genome-sequencing of the obligate symbiotic, Mycoplasma-related endobacteria of arbuscular mycorrhizal fungi to uncover their function and coevolution.

丛枝菌根真菌（AMF）是陆地植物的共生体，已有4亿多年的历史，已知其细胞质中含有革兰氏阳性内细菌，传统上称为细菌样生物（BLOs）。最近，我们可以证明AMF- blos的16S rDNA序列（来自高度多样化的AMF谱系）都属于Mollicutes类的一个古老的单系进化枝。尽管不可培养的BLOs在AMF中一定起着重要的作用，可能是细胞器一样的作用，但它们的功能迄今为止尚不清楚。在这个项目中，我们的目标是实现BLOs基因组的完整测序，以了解它们在重要的AM共生中的功能。在单个AMF孢子中，BLOs具有遗传多态性。为了探索和注释它们的宏基因组和个体基因组序列，我们将使用两个明确的AMF分离株，并结合宏基因组学、单细胞分选、全基因组扩增和新的测序技术。这将对生物组织的能力以及环境和进化适应提供全面的见解。关于这些难以捉摸的细菌及其宿主的前所未有的数据在农业应用方面也非常有趣。我们预计BLO基因组序列信息可能揭示必需或有利的代谢途径、抗生素合成或耐药性、AM进化的假定意义（例如，通过水平基因转移）以及一些不可预见的方面，如效应分泌的暗示。

Arbuscular mycorrhizal fungi (AMF), symbionts of land plants for >400 million years (My), are known to host in their cytoplasm Gram-positive endobacteria traditionally called bacterium-like organisms (BLOs). Recently, we could show that 16S rDNA sequences of AMF-BLOs (from highly diverse AMF lineages) all fall in a >400 My old monophyletic clade in the class Mollicutes. Despite the fact that the uncultivable BLOs must play an important, maybe organelle-like role in AMF, their function is thus far unknown. In this project, we aim to achieve a full sequencing of the genomes of BLOs to founder understanding their functioning in the important AM symbiosis. Within a single AMF spore BLOs are genetically polymorphic. To explore and annotate their metagenome and individual genome sequences, we will use two well defined AMF isolates and combine metagenomics, single cell sorting, whole genome amplification and new sequencing technologies. This will provide comprehensive insights into the capacities and environmental and evolutionary adaptations of BLOs. The unprecedented data regarding these elusive bacteria and their hosts potentially are highly interesting also for applied, agricultural aspects. We anticipate that BLO genome sequence information may reveal essential or advantageous metabolic pathways, antibiotics-synthesis or -resistance, putative significance for AM evolution (e.g., by horizontal gene transfer), and several unforeseeable aspects, like hints for effector secretion.