INRA, UMR1136 INRA-Nancy Université, «Interactions Arbres/Micro-organismes», Centre de Nancy, IFR110, 54280 Champenoux, France. Department of Plant Sciences, University of Oxford, Oxford OX1 3RB, UK. Department of Microbiology and Immunology, Dartmouth Medical School, 208 Vail Building, Hanover, NH 03755, USA.
Environ Microbiol Rep. 2011 Apr;3(2):203-10. doi: 10.1111/j.1758-2229.2010.00209.x. Epub 2010 Sep 1.
The Mycorrhiza Helper Bacterium (MHB) Pseudomonas fluorescens BBc6R8 promotes the ectomycorrhizal symbiosis between Douglas fir roots and Laccaria bicolor. In this study, we identified a non-flagellar type III secretion system (T3SS) in the draft genome of BBc6R8 similar to that described in the biocontrol strain P. fluorescens SBW25. We examined whether this T3SS plays a role in the BBc6R8 mycorrhizal helper effect by creating a deletion in the rscRST genes encoding the central channel of the injectisome. The in vitro effect of BBc6R8 T3SS mutants on the radial growth rate of L. bicolor was unchanged compared with the parental strain. In contrast, T3SS mutants were unable to promote mycorrhization, suggesting that type III secretion plays an important role in the mycorrhizal helper effect of P. fluorescens BBc6R8 independent of the promotion of hyphal growth that BBc6R8 exhibits in vitro.
菌根辅助菌（MHB）荧光假单胞菌 BBc6R8 促进了花旗松根系和双色蜡蘑之间的外生菌根共生。在这项研究中，我们在 BBc6R8 的草图基因组中鉴定出了一种非鞭毛型 III 型分泌系统（T3SS），类似于在生物防治菌株 P. fluorescens SBW25 中描述的 T3SS。我们通过创建 rscRST 基因的缺失来检验该 T3SS 是否在 BBc6R8 的菌根辅助效应中发挥作用，这些基因编码注入器的中央通道。与亲本菌株相比，BBc6R8 T3SS 突变体在体外对双色蜡蘑径向生长率的影响没有变化。相比之下，T3SS 突变体无法促进菌根化，这表明 III 型分泌在 P. fluorescens BBc6R8 的菌根辅助效应中发挥着重要作用，而与 BBc6R8 在体外表现出的促进菌丝生长无关。
