Department of Plant Medicine, Chungbuk National University, Cheongju, Chungbuk 361-763, Korea.
Department of Plant Molecular Systems Biotech & Crop Biotech Institute, KyungHee University, Yongin 446-701, Korea.
Plant Pathol J. 2013 Dec;29(4):364-73. doi: 10.5423/PPJ.OA.06.2013.0057.
It has been known that most regulation of pathogenicity factor (rpf) genes in xanthomonads regulates virulence in response to the diffusible signal factor, DSF. Although many rpf genes have been functionally characterized, the function of rpfE is still unknown. We cloned the rpfE gene from a Xanthomonas oryzae pv. oryzae (Xoo) Korean race KACC10859 and generated mutant strains to elucidate the role of RpfE with respect to the rpf system. Through experiments using the rpfE-deficient mutant strain, we found that mutation in rpfE gene in Xoo reduced virulence, swarm motility, and production of virulence factors such as cellulase and extracellular polysaccharide. Disease progress by the rpfE-deficient mutant strain was significantly slowed compared to disease progress by the wild type and the number of the rpfE-deficient mutant strain was lower than that of the wild type in the early phase of infection in the inoculated rice leaf. The rpfE mutant strain was unable to utilize sucrose or xylose as carbon sources efficiently in culture. The mutation in rpfE, however, did not affect DSF synthesis. Our results suggest that the rpfE gene regulates the virulence of Xoo under different nutrient conditions without change of DSF production.
已知黄单胞菌中大多数致病性因子（rpf）基因的调控是响应可扩散信号因子（DSF）来调节毒性的。尽管许多 rpf 基因的功能已经得到了表征，但 rpfE 的功能仍然未知。我们从一株来自韩国的水稻黄单胞菌（Xoo）KACC10859 克隆了 rpfE 基因，并生成了突变株，以阐明 RpfE 在 rpf 系统中的作用。通过使用 rpfE 缺失突变株的实验，我们发现 Xoo 中 rpfE 基因的突变降低了毒性、群集运动性以及纤维素酶和胞外多糖等毒力因子的产生。与野生型相比，rpfE 缺失突变株引起的病害进展明显减缓，在接种水稻叶片的感染早期，rpfE 缺失突变株的数量低于野生型。rpfE 突变株在培养中不能有效地利用蔗糖或木糖作为碳源。然而，rpfE 突变并不影响 DSF 的合成。我们的结果表明，rpfE 基因在不同的营养条件下调节 Xoo 的毒性，而不改变 DSF 的产生。
