Plant Molecular and Cellular Biology Program (PMCB), Horticultural Sciences Department, University of Florida, Gainesville, FL 32611, USA.
BMC Plant Biol. 2011 Nov 11;11:159. doi: 10.1186/1471-2229-11-159.
Citrus canker disease caused by the bacterial pathogen Xanthomonas citri subsp. citri (Xcc) has become endemic in areas where high temperature, rain, humidity, and windy conditions provide a favourable environment for the dissemination of the bacterium. Xcc is pathogenic on many commercial citrus varieties but appears to elicit an incompatible reaction on the citrus relative Fortunella margarita Swing (kumquat), in the form of a very distinct delayed necrotic response. We have developed subtractive libraries enriched in sequences expressed in kumquat leaves during both early and late stages of the disease. The isolated differentially expressed transcripts were subsequently sequenced. Our results demonstrate how the use of microarray expression profiling can help assign roles to previously uncharacterized genes and elucidate plant pathogenesis-response related mechanisms. This can be considered to be a case study in a citrus relative where high throughput technologies were utilized to understand defence mechanisms in Fortunella and citrus at the molecular level.
cDNAs from sequenced kumquat libraries (ESTs) made from subtracted RNA populations, healthy vs. infected, were used to make this microarray. Of 2054 selected genes on a customized array, 317 were differentially expressed (P < 0.05) in Xcc challenged kumquat plants compared to mock-inoculated ones. This study identified components of the incompatible interaction such as reactive oxygen species (ROS) and programmed cell death (PCD). Common defence mechanisms and a number of resistance genes were also identified. In addition, there were a considerable number of differentially regulated genes that had no homologues in the databases. This could be an indication of either a specialized set of genes employed by kumquat in response to canker disease or new defence mechanisms in citrus.
Functional categorization of kumquat Xcc-responsive genes revealed an enhanced defence-related metabolism as well as a number of resistant response-specific genes in the kumquat transcriptome in response to Xcc inoculation. Gene expression profile(s) were analyzed to assemble a comprehensive and inclusive image of the molecular interaction in the kumquat/Xcc system. This was done in order to elucidate molecular mechanisms associated with the development of the hypersensitive response phenotype in kumquat leaves. These data will be used to perform comparisons among citrus species to evaluate means to enhance the host immune responses against bacterial diseases.
由细菌病原体柑橘溃疡病菌（Xanthomonas citri subsp. citri，Xcc）引起的柑橘溃疡病已在高温、多雨、高湿度和多风等有利于细菌传播的地区流行。Xcc 可侵染许多商业柑橘品种，但似乎会在柑橘亲缘植物金桔（ Fortunella margarita Swing，金桔）上引起不亲和反应，表现为非常明显的延迟坏死反应。我们构建了在柑橘溃疡病早期和晚期表达的金桔叶片差异表达基因的消减文库。随后对分离的差异表达转录本进行了测序。研究结果表明，利用基因芯片表达谱分析可以帮助鉴定以前未鉴定基因的功能，并阐明与植物发病机制反应相关的机制。这可以被认为是柑橘亲缘植物的一个案例研究，在该研究中利用高通量技术从分子水平上理解金桔和柑橘的防御机制。
从健康和感染的柑橘溃疡病菌处理的金桔 RNA 群体构建的消减文库的 cDNA 用于制作此基因芯片。在定制的基因芯片上选择的 2054 个基因中，有 317 个基因在柑橘溃疡病菌处理的金桔植株中与 mock 接种的金桔植株相比差异表达（P < 0.05）。本研究鉴定了与不亲和反应相关的成分，如活性氧（ROS）和程序性细胞死亡（PCD）。还鉴定了一些共同的防御机制和一些抗性基因。此外，还有相当数量的差异调控基因在数据库中没有同源物。这可能表明金桔在应对溃疡病时使用了一组专门的基因，或者柑橘中存在新的防御机制。
金桔 Xcc 响应基因的功能分类揭示了金桔转录组中增强的防御相关代谢以及在柑橘溃疡病菌接种后金桔中一些抗性反应特异性基因。对基因表达谱进行了分析，以组装金桔/Xcc 系统中分子相互作用的全面和综合图像。这是为了阐明与金桔叶片过敏反应表型发展相关的分子机制。这些数据将用于在柑橘属植物中进行比较，以评估增强宿主对细菌性疾病免疫反应的方法。
