Salvioli di Fossalunga Alessandra, Lipuma Justine, Venice Francesco, Dupont Laurence, Bonfante Paola
Department of Life Sciences and Systems Biology, University of Torino, Torino, Italy.
Institut Sophia Agrobiotech (ISA), INRA UMR 1355, CNRS UMR 7254, Université de Nice Sophia Antipolis, Sophia Antipolis, France.
ISME J. 2017 Oct;11(10):2394-2398. doi: 10.1038/ismej.2017.84. Epub 2017 May 26.
Arbuscular mycorrhizal fungi (AMF) are widespread root symbionts that perform important ecological services, such as improving plant nutrient and water acquisition. Some AMF from the Gigasporaceae family host a population of endobacteria, Candidatus Glomeribacter gigasporarum (Cagg). The analysis of the Cagg genome identified six putative toxin-antitoxin modules (TAs), consisting of pairs of stable toxins and unstable antitoxins that affect diverse physiological functions. Sequence analysis suggested that these TA modules were acquired by horizontal transfer. Gene expression patterns of two TAs (yoeB/yefM and chpB/chpS) changed during the fungal life cycle, with the expression during the pre-symbiotic phase higher than during the symbiosis with the plant host. The heterologous expression in Escherichia coli demonstrated the functionality only for the YoeB-YefM pair. On the basis of these observations, we speculate that TA modules might help Cagg adapt to its intracellular habitat, coordinating its proliferation with the physiological state of the AMF host.
丛枝菌根真菌（AMF）是广泛存在的根系共生体，能发挥重要的生态服务功能，比如改善植物对养分和水分的获取。一些巨孢囊霉科的AMF宿主有一种内生细菌种群，即暂定名为巨大球囊杆菌（Cagg）。对Cagg基因组的分析确定了六个假定的毒素-抗毒素模块（TA），它们由成对的稳定毒素和不稳定抗毒素组成，影响多种生理功能。序列分析表明这些TA模块是通过水平转移获得的。两个TA（yoeB/yefM和chpB/chpS）的基因表达模式在真菌生命周期中发生变化，共生前阶段的表达高于与植物宿主共生期间的表达。在大肠杆菌中的异源表达表明只有YoeB-YefM对具有功能。基于这些观察结果，我们推测TA模块可能有助于Cagg适应其细胞内栖息地，使其增殖与AMF宿主的生理状态相协调。
