Centre for Research in Plant Science, The University of the West of England, Bristol, UK.
Mol Plant Microbe Interact. 2010 Oct;23(10):1294-302. doi: 10.1094/MPMI-05-10-0114.
Pseudomonas syringae pv. phaseolicola is the seed borne causative agent of halo blight in the common bean Phaseolus vulgaris. Pseudomonas syringae pv. phaseolicola race 4 strain 1302A contains the avirulence gene hopAR1 (located on a 106-kb genomic island, PPHGI-1, and earlier named avrPphB), which matches resistance gene R3 in P. vulgaris cultivar Tendergreen (TG) and causes a rapid hypersensitive reaction (HR). Here, we have fluorescently labeled selected Pseudomonas syringae pv. phaseolicola 1302A and 1448A strains (with and without PPHGI-1) to enable confocal imaging of in-planta colony formation within the apoplast of resistant (TG) and susceptible (Canadian Wonder [CW]) P. vulgaris leaves. Temporal quantification of fluorescent Pseudomonas syringae pv. phaseolicola colony development correlated with in-planta bacterial multiplication (measured as CFU/ml) and is, therefore, an effective means of monitoring Pseudomonas syringae pv. phaseolicola endophytic colonization and survival in P. vulgaris. We present advances in the application of confocal microscopy for in-planta visualization of Pseudomonas syringae pv. phaseolicola colony development in the leaf mesophyll to show how the HR defense response greatly affects colony morphology and bacterial survival. Unexpectedly, the presence of PPHGI-1 was found to cause a reduction of colony development in susceptible P. vulgaris CW leaf tissue. We discuss the evolutionary consequences that the acquisition and retention of PPHGI-1 brings to Pseudomonas syringae pv. phaseolicola in planta.
丁香假单胞菌 pv. phaseolicola 是普通菜豆 Phaseolus vulgaris 中晕斑病的种子传播病原体。丁香假单胞菌 pv. phaseolicola 4 型菌株 1302A 含有无毒基因 hopAR1（位于 106kb 基因组岛上，PPHGI-1，早期命名为 avrPphB），与菜豆品种 Tendergreen（TG）中的抗性基因 R3 匹配，并引起快速过敏反应（HR）。在这里，我们对选定的丁香假单胞菌 pv. phaseolicola 1302A 和 1448A 菌株（带有和不带有 PPHGI-1）进行了荧光标记，以实现对抗性（TG）和易感（加拿大奇迹[CW]）菜豆叶片外质体中细菌群体形成的共聚焦成像。荧光假单胞菌 pv. phaseolicola 菌落发育的时间定量与植物内细菌增殖（以 CFU/ml 测量）相关，因此是监测假单胞菌 pv. phaseolicola 在菜豆中的内生定殖和存活的有效方法。我们介绍了共聚焦显微镜在叶片叶肉中观察假单胞菌 pv. phaseolicola 菌落发育的应用进展，以展示 HR 防御反应如何极大地影响菌落形态和细菌存活。出乎意料的是，发现 PPHGI-1 的存在会导致易感菜豆 CW 叶片组织中菌落发育减少。我们讨论了 PPHGI-1 的获得和保留给植物内丁香假单胞菌 pv. phaseolicola 带来的进化后果。
