Expression data from Pseudomonas aeruginosa infiltrated into resistant and susceptible cultivars of Nicotiana tabacum.

Although Pseudomonas aeruginosa is an opportunistic pathogen that does not often naturally infect alternate hosts such as plants, the plant-P. aeruginosa model has become a widely recognized system for identifying new virulence determinants and studying pathogenesis of this organism. Here we examine how both host factors and P. aeruginosa PAO1 gene expression are affected in planta after infiltration into incompatible and compatible cultivars of tobacco (Nicotiana tabacum L.) Nicotiana tabacum has a resistance gene (N) against tobacco mosaic virus; and although resistance to PAO1 infection correlated to the presence of a dominant N-gene, our data suggests that it is not a factor in resistance against Pseudomonas. We did observe that the resistant tobacco cultivar had higher basal levels of salicylic acid, and a stronger salicylic acid response upon infiltration of PAO1. Salicylic acid acts as a signal to activate defense responses in plants, limiting the spread of the pathogen and preventng access to nutrients. It has also been shown to have direct virulence modulating effects on P. aeruginosa. We also examined host effects on the pathogen by analyzing global gene expression profiles of bacteria removed from the intracellular fluid of the two plant hosts. We discovered that the availability of micronutrients, particularly sulfate and Pi, are important factors in in planta pathogenesis, and that the amounts of these nutrients made available to the bacteria may in turn have an effect on virulence gene expression. Indeed, there are several reports suggesting that P. aeruginosa virulence is influenced in mammalian hosts by the availability of iron and by levels of O2. Keywords: comparative genomic hybridization, disease state analysis Pseudomonas aeruginosa cells were removed from leaf tissue 24 hours post-infiltration and RNA was directly extracted from these cells. Comparisons are between cells removed from a susceptible cultivar of Nicotiana tabacum (cv. Samsun) and a resistant cultivar (cv. Xanthi). Three biological replicates per cultivar were analyzed.

铜绿假单胞菌（Pseudomonas aeruginosa）是一种机会致病菌，通常不会自然侵染植物等非天然宿主，但植物-铜绿假单胞菌模型已成为鉴定该菌新型毒力决定因子、研究其致病机制的公认研究体系。本研究探究了将铜绿假单胞菌PAO1分别浸润接种到烟草（Nicotiana tabacum L.）的亲和与非亲和品种后，宿主因子与该菌的基因表达如何受到植物体内环境的影响。烟草本身携带抗烟草花叶病毒的N基因；尽管对PAO1的抗性与显性N基因的存在相关，但本研究数据显示，该基因并非铜绿假单胞菌抗性的影响因子。本研究确实观察到，抗病烟草品种的水杨酸基础水平更高，且在PAO1浸润后其水杨酸响应更为强烈。水杨酸作为信号分子可激活植物的防御反应，限制病原菌扩散并阻碍其获取营养物质；同时已有研究表明，水杨酸可直接调控铜绿假单胞菌的毒力。本研究还通过分析从两种烟草宿主的细胞内液中分离得到的细菌的全局基因表达谱，探究了宿主对病原菌的影响。本研究发现，微量营养元素的可获得性——尤其是硫酸盐与无机磷酸盐（Pi）——是植物体内致病过程的重要影响因素，而病原菌可获取的此类营养物质水平又可反过来调控毒力基因的表达。事实上，已有多项研究表明，铜绿假单胞菌的毒力在哺乳动物宿主中会受到铁可获得性与氧气水平的调控。
关键词：比较基因组杂交（comparative genomic hybridization），疾病状态分析
实验中，我们于浸润接种24小时后从烟草叶片组织中分离铜绿假单胞菌，并直接从这些细菌中提取RNA。本研究的比较分析样本分别取自感病烟草品种（栽培种Samsun）与抗病烟草品种（栽培种Xanthi），每个品种设置3次生物学重复。