Department of Agricultural Sciences, University of Helsinki, Helsinki, Finland.
College of Plant Protection, Hebei Agricultural University, Hebei, China.
PLoS One. 2022 Aug 29;17(8):e0273481. doi: 10.1371/journal.pone.0273481. eCollection 2022.
Dickeya solani is a soft rot bacterium with high virulence. In potato, D. solani, like the other potato-infecting soft rot bacteria, causes rotting and wilting of the stems and rotting of tubers in the field and in storage. Latent, asymptomatic infections of potato tubers are common in harvested tubers, and if the storage conditions are not optimal, the latent infection turns into active rotting. We characterized potato gene expression in artificially inoculated tubers in nonsymptomatic, early infections 1 and 24 hours post-inoculation (hpi) and compared the results to the response in symptomatic tuber tissue 1 week (168 hpi) later with RNA-Seq. In the beginning of the infection, potato tubers expressed genes involved in the detection of the bacterium through pathogen-associated molecular patterns (PAMPs), which induced genes involved in PAMPs-triggered immunity, resistance, production of pathogenesis-related proteins, ROS, secondary metabolites and salicylic acid (SA) and jasmonic acid (JA) biosynthesis and signaling genes. In the symptomatic tuber tissue one week later, the PAMPs-triggered gene expression was downregulated, whereas primary metabolism was affected, most likely leading to free sugars fueling plant defense but possibly also aiding the growth of the pathogen. In the symptomatic tubers, pectic enzymes and cell wall-based defenses were activated. Measurement of hormone production revealed increased SA concentration and almost no JA in the asymptomatic tubers at the beginning of the infection and high level of JA and reduced SA in the symptomatic tubers one week later. These findings suggest that potato tubers rely on different defense strategies in the different phases of D. solani infection even when the infection takes place in fully susceptible plants incubated in conditions leading to rotting. These results support the idea that D. solani is a biotroph rather than a true necrotroph.
丁香假单胞菌是一种具有高毒性的软腐细菌。在马铃薯中，像其他感染马铃薯的软腐细菌一样，丁香假单胞菌会导致田间和贮藏期茎部腐烂和萎蔫，以及块茎腐烂。在收获的块茎中，马铃薯块茎的潜伏、无症状感染很常见，如果贮藏条件不理想，潜伏感染会转变为活跃腐烂。我们通过 RNA-Seq 对人工接种的无症状、早期感染马铃薯块茎（接种后 1 小时和 24 小时）的马铃薯基因表达进行了特征描述，并将结果与 1 周后（168 小时）出现症状的块茎组织的反应进行了比较。在感染初期，马铃薯块茎通过病原体相关分子模式（PAMPs）表达了检测细菌的基因，这些基因诱导了与 PAMPs 触发的免疫、抗性、病程相关蛋白、活性氧（ROS）、次生代谢物和水杨酸（SA）和茉莉酸（JA）生物合成和信号转导基因的表达。1 周后，出现症状的块茎组织中，PAMPs 触发的基因表达下调，而初级代谢受到影响，这很可能导致游离糖为植物防御提供燃料，但也可能有助于病原体的生长。在出现症状的块茎中，果胶酶和细胞壁防御被激活。激素产生的测量结果表明，在感染初期无症状的块茎中，SA 浓度增加，JA 几乎没有，1 周后出现症状的块茎中 JA 水平升高，SA 浓度降低。这些发现表明，即使在易感性完全的植物中，在导致腐烂的条件下培养，马铃薯块茎在丁香假单胞菌感染的不同阶段也会依赖不同的防御策略。这些结果支持了丁香假单胞菌是一种生物营养体而不是真正的坏死营养体的观点。
