Department of Agriculture and Biology, Shanghai Jiao Tong University, China.
Arch Microbiol. 2012 Apr;194(4):281-91. doi: 10.1007/s00203-011-0758-x. Epub 2011 Oct 11.
Xanthomonas oryzae pv. oryzicola is the causal agent of bacterial leaf streak in rice and injects repertoires of T3S effectors (T3SEs), which are normally regulated by a global regulator HrpX, into plant cells to suppress plant innate immunity for disease development. To establish a visualization technique to identify HrpX regulon genes in this pathogen, we chose six known or unknown T3SE genes of X. oryzae pv. oryzicola (strain RS105) as the targets in this report. The promoters of these candidates, whether or not containing a PIP-box, were fused with the gfp (green fluorescent protein) reporter gene, and the gfp reporters were introduced into the wild-type RS105 and the hrpX mutant RΔhrpX. GFP expression in the wild-type strain could be observed under fluorescence microscopy, but fluorescence was not observed in the hrpX mutant. Consequently, transcription and secretion detection demonstrated that these HrpX regulon members were repressed when hrpX was mutated and were not secreted into the hrp-inducing medium XOM3 because of a mutation in hrcV (T3SS deficient). These data suggest that the gfp reporter system is a feasible visualization tool for the identification of HrpX regulon genes and discovery of new T3SEs in the X. oryzae pv. oryzicola-rice pathosystem.
稻黄单胞菌叶斑病菌是水稻细菌性条斑病的致病菌，它向植物细胞中注射 T3S 效应器（T3SEs）的 repertoire，这些效应器通常由全局调控因子 HrpX 调控，以抑制植物先天免疫从而促进疾病发展。为了在该病原体中建立可视化技术来鉴定 HrpX 调控基因，我们选择了稻黄单胞菌叶斑病菌（菌株 RS105）中六个已知或未知的 T3SE 基因作为本报告的靶标。这些候选物的启动子，无论是否包含 PIP 盒，均与 GFP（绿色荧光蛋白）报告基因融合，GFP 报告基因被引入野生型 RS105 和 hrpX 突变体 RΔhrpX。在荧光显微镜下可以观察到野生型菌株中的 GFP 表达，但在 hrpX 突变体中未观察到荧光。因此，转录和分泌检测表明，当 hrpX 突变时，这些 HrpX 调控基因被抑制，并且由于 hrcV（T3SS 缺陷）突变，它们不能分泌到 hrp 诱导培养基 XOM3 中。这些数据表明，GFP 报告系统是鉴定稻黄单胞菌叶斑病菌 - 水稻病理系统中 HrpX 调控基因和发现新 T3SE 的可行可视化工具。
