Cyclic Lipopeptides of Bacillus amyloliquefaciens subsp plantarum Colonizing the Lettuce Rhizosphere Enhance Plant Defense Responses Toward the Bottom Rot Pathogen Rhizoctonia solani
Cyclic Lipopeptides of Bacillus amyloliquefaciens subsp plantarum Colonizing the Lettuce Rhizosphere Enhance Plant Defense Responses Toward the Bottom Rot Pathogen Rhizoctonia solani
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DOI：
10.1094/mpmi-03-15-0066-r
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发表时间：
2015-09-01
影响因子：
3.5
通讯作者：
Hartmann, Anton
中科院分区：
文献类型：
--
作者：
Chowdhury, Soumitra Paul;Uhl, Jenny;Hartmann, Anton
市售的解淀粉芽孢杆菌FZB 42能够显著地减少由立枯丝核菌引起的莴苣底腐。为了解FZB 42与R.本研究采用FZB-42细菌接种生菜，接种R.索拉尼共聚焦激光扫描显微镜观察发现，FZB 42能延缓R.植物上的solani为了显示在这些原位条件下产生的FZB 42的次级代谢产物，我们开发了一种超高效液相色谱-飞行时间质谱法为基础的方法，并确定了表面活性素，芬枯草菌素，和芽孢杆菌霉素D在莴苣根际。我们推测，脂肽和聚酮化合物除了对R. Solani等，并使用基于定量实时聚合酶链反应的测定法来检测莴苣中涉及防御信号传导途径的标记基因。在细菌化的植物中观察到响应于随后的病原体攻击的PDF1.2的显著更高表达，表明FZB 42可以增强莴苣对真菌病原体的防御反应。为了确定表面活性素或其他nonribosomally合成的次级代谢产物是否可以引起所观察到的增强防御基因的表达，我们研究了两个突变体FZB 42缺乏生产的表面活性素和脂肽和聚酮，通过表达分析和盆栽实验。在表面活性素和其他非核糖体合成的次级代谢产物的情况下，没有增强的PDF 1.2介导的响应病原体的挑战。盆栽试验结果表明，与FZB 42野生型相比，突变体未能降低莴苣的发病率，表明表面活性素以及其他非核糖体合成的次生代谢产物在实际的病害抑制和莴苣健康中发挥作用。总之，我们的研究表明，FZB 42的非核糖体合成的次生代谢产物实际上是在莴苣根际产生的，并通过介导植物防御基因表达对病原体R.索拉尼
The commercially available inoculant Bacillus amyloliquefaciens FZB42 is able to considerably reduce lettuce bottom rot caused by Rhizoctonia solani. To understand the interaction between FZB42 and R. solani in the rhizosphere of lettuce, we used an axenic system with lettuce bacterized with FZB42 and inoculated with R. solani. Confocal laser scanning microscopy showed that FZB42 could delay the initial establishment of R. solani on the plants. To show which secondary metabolites of FZB42 are produced under these in-situ conditions, we developed an ultra-high performance liquid chromatography coupled to time of flight mass spectrometry based method and identified surfactin, fengycin, and bacillomycin D in the lettuce rhizosphere. We hypothesized that lipopeptides and polyketides play a role in enhancing the plant defense responses in addition to the direct antagonistic effect toward R. solani and used a quantitative real-time polymerase chain reaction based assay for marker genes involved in defense signaling pathways in lettuce. A significant higher expression of PDF 1.2 observed in the bacterized plants in response to subsequent pathogen challenge showed that FZB42 could enhance the lettuce defense response toward the fungal pathogen. To identify if surfactin or other nonribosomally synthesized secondary metabolites could elicit the observed enhanced defense gene expression, we examined two mutants of FZB42 deficient in production of surfactin and the lipopetides and polyketides, by expression analysis and pot experiments. In the absence of surfactin and other nonribosomally synthesized secondary metabolites, there was no enhanced PDF 1.2 mediated response to the pathogen challenge. Pot experiment results showed that the mutants failed to reduce disease incidence in lettuce as compared with the FZB42 wild type, indicating, that surfactin as well as other nonribosomally synthesized secondary metabolites play a role in the actual disease suppression and on lettuce health. In conclusion, our study showed that nonribosomally synthesized secondary metabolites of FZB42 are actually produced in the lettuce rhizosphere and contribute to the disease suppression by mediating plant defense gene expression toward the pathogen R. solani.