UMR 5096 IRD-CNRS-Université de Perpignan, Laboratoire Génome et Développement des Plantes, Institut de Recherche pour le Développement, 911 Avenue Agropolis BP 64501, 34394 Montpellier Cedex 5, France.
BMC Microbiol. 2010 Jun 11;10:170. doi: 10.1186/1471-2180-10-170.
Bacterial leaf blight causes significant yield losses in rice crops throughout Asia and Africa. Although both the Asian and African strains of the pathogen, Xanthomonas oryzae pv. oryzae (Xoo), induce similar symptoms, they are nevertheless genetically different, with the African strains being more closely related to the Asian X. oryzae pv. oryzicola (Xoc).
Changes in gene expression of the African Xoo strain MAI1 in the susceptible rice cultivar Nipponbare were profiled, using an SSH Xoo DNA microarray. Microarray hybridization was performed comparing bacteria recovered from plant tissues at 1, 3, and 6 days after inoculation (dai) with bacteria grown in vitro. A total of 710 bacterial genes were found to be differentially expressed, with 407 up-regulated and 303 down-regulated. Expression profiling indicated that less than 20% of the 710 bacterial transcripts were induced in the first 24 h after inoculation, whereas 63% were differentially expressed at 6 dai. The 710 differentially expressed genes were one-end sequenced. 535 sequences were obtained from which 147 non-redundant sequences were identified. Differentially expressed genes were related to metabolism, secretion and transport, pathogen adherence to plant tissues, plant cell-wall degradation, IS elements, and virulence. In addition, various other genes encoding proteins with unknown function or showing no similarity to other proteins were also induced. The Xoo MAI1 non-redundant set of sequences was compared against several X. oryzae genomes, revealing a specific group of genes that was present only in MAI1. Numerous IS elements were also found to be differentially expressed. Quantitative real-time PCR confirmed 86% of the identified profile on a set of 14 genes selected according to the microarray analysis.
This is the first report to compare the expression of Xoo genes in planta across different time points during infection. This work shows that as-yet-unidentified and potentially new virulence factors are appearing in an emerging African pathogen. It also confirms that African Xoo strains do differ from their Asian counterparts, even at the transcriptional level.
细菌性条斑病在亚洲和非洲的水稻作物中造成了重大的产量损失。尽管病原体稻黄单胞菌亚洲致病变种（Xanthomonas oryzae pv. oryzae，Xoo）的亚洲株系和非洲株系引起的症状相似，但它们在遗传上是不同的，非洲株系与亚洲的稻黄单胞菌非洲致病变种（Xanthomonas oryzae pv. oryzicola，Xoc）更为接近。
使用 SSH Xoo DNA 微阵列对易感水稻品种 Nipponbare 中非洲 Xoo 菌株 MAI1 的基因表达变化进行了分析。将接种后 1、3 和 6 天（dai）从植物组织中回收的细菌与体外培养的细菌进行比较，进行了微阵列杂交。共发现 710 个细菌基因差异表达，其中 407 个上调，303 个下调。表达谱分析表明，接种后前 24 小时诱导的细菌转录物不到 710 个的 20%，而 63%在 6 dai 时差异表达。对 710 个差异表达的基因进行了一端测序。从获得的 535 个序列中鉴定出 147 个非冗余序列。差异表达的基因与代谢、分泌和运输、病原体对植物组织的附着、植物细胞壁降解、IS 元件和毒力有关。此外，还诱导了许多其他编码具有未知功能或与其他蛋白质没有相似性的蛋白质的基因。将 Xoo MAI1 的非冗余序列集与几个稻黄单胞菌基因组进行比较，发现了一个仅存在于 MAI1 中的特定基因群。还发现了大量差异表达的 IS 元件。根据微阵列分析选择的 14 个基因的一组，定量实时 PCR 证实了 86%的鉴定图谱。
这是首次比较感染过程中不同时间点 Xoo 基因在植物体内的表达情况的报告。这项工作表明，尚未确定的潜在新毒力因子出现在一种新兴的非洲病原体中。它还证实，非洲 Xoo 菌株即使在转录水平上也与亚洲菌株不同。
