Songwattana Pongpan, Noisangiam Rujirek, Teamtisong Kamonluck, Prakamhang Janpen, Teulet Albin, Tittabutr Panlada, Piromyou Pongdet, Boonkerd Nantakorn, Giraud Eric, Teaumroong Neung
School of Biotechnology, Institute of Agricultural Technology, Suranaree University of TechnologyNakhon Ratchasima, Thailand.
National Bureau of Agricultural Commodity and Food Standards, Ministry of Agriculture and CooperativesBangkok, Thailand.
Front Microbiol. 2017 Sep 20;8:1810. doi: 10.3389/fmicb.2017.01810. eCollection 2017.
The sp. DOA9 strain isolated from a paddy field has the ability to nodulate a wide spectrum of legumes. Unlike other bradyrhizobia, this strain has a symbiotic plasmid harboring , , and type 3 secretion system (T3SS) genes. This T3SS cluster contains all the genes necessary for the formation of the secretory apparatus and the transcriptional activator (TtsI), which is preceded by a -box motif. An search predicted 14 effectors putatively translocated by this T3SS machinery. In this study, we explored the role of the T3SS in the symbiotic performance of DOA9 by evaluating the ability of a T3SS mutant (Ω) to nodulate legumes belonging to Dalbergioid, Millettioid, and Genistoid tribes. Among the nine species tested, four (, , , and ) responded positively to the mutation (ranging from suppression of plant defense reactions, an increase in the number of nodules and a dramatic improvement in nodule development and infection), one () responded negatively (fewer nodules and less nitrogen fixation) and four species (, , , and ) displayed no phenotype. We also tested the role of the T3SS in the ability of the DOA9 strain to endophytically colonize rice roots, but detected no effect of the T3SS mutation, in contrast to what was previously reported in the SUTN9-2 strain. Taken together, these data indicate that DOA9 contains a functional T3SS that interferes with the ability of the strain to interact symbiotically with legumes but not with rice.
从稻田中分离出的DOA9菌株能够使多种豆科植物结瘤。与其他慢生根瘤菌不同，该菌株具有一个共生质粒，其中含有、和3型分泌系统（T3SS）基因。这个T3SS基因簇包含了分泌装置形成所需的所有基因以及转录激活因子（TtsI），其前面有一个-box基序。一项搜索预测有14种效应蛋白可能由这个T3SS机制转运。在本研究中，我们通过评估T3SS突变体（Ω）使属于黄檀族、崖豆族和染料木族的豆科植物结瘤的能力，探究了T3SS在DOA9共生性能中的作用。在所测试的9个物种中，有4个（、、和）对突变有正向反应（范围从抑制植物防御反应、增加根瘤数量以及显著改善根瘤发育和感染），1个（）有负向反应（根瘤较少且固氮较少），还有4个物种（、、和）没有表现出表型。我们还测试了T3SS在DOA9菌株内生定殖水稻根能力中的作用，但与之前在SUTN9 - 2菌株中报道的情况相反，未检测到T3SS突变有任何影响。综上所述，这些数据表明DOA9含有一个功能性T3SS，它会干扰该菌株与豆科植物共生互作的能力，但不影响与水稻的共生互作。
