1 Department of Entomology and Plant Pathology, Auburn University, Auburn, AL 36849, U.S.A.; and.
2 Department of Biological Sciences, Auburn University.
Mol Plant Microbe Interact. 2017 Nov;30(11):896-905. doi: 10.1094/MPMI-07-17-0161-R. Epub 2017 Sep 19.
MopB is a major outer membrane protein (OMP) in Xylella fastidiosa, a bacterial plant pathogen that causes losses on many economically important crops. Based on in silico analysis, the uncharacterized MopB protein of X. fastidiosa contains a β-barrel structure with an OmpA-like domain and a predicted calcium-binding motif. Here, MopB function was studied by mutational analysis taking advantage of the natural competence of X. fastidiosa. Mutants of mopB were constructed in two different X. fastidiosa strains, the type strain Temecula and the more virulent WM1-1. Deletion of the mopB gene impaired cell-to-cell aggregation, surface attachment, and biofilm formation in both strains. Interestingly, mopB deletion completely abolished twitching motility. Electron microscopy of the bacterial cell surface revealed that mopB deletion eliminated type IV and type I pili formation, potentially caused by destabilization of the outer membrane. Both mopB mutants showed reduced virulence using tobacco (Nicotiana tabacum) as a host under greenhouse conditions. These results suggest that MopB has pleiotropic functions in biofilm formation and twitching motility and is important for virulence of X. fastidiosa.
MopB 是木质部难养菌（Xylella fastidiosa）的一种主要外膜蛋白（OMP），这种细菌是一种植物病原体，会导致许多经济重要作物的损失。基于计算机分析，木质部难养菌的未鉴定 MopB 蛋白含有一个β-桶结构，带有一个类似于 OmpA 的结构域和一个预测的钙结合基序。在这里，利用木质部难养菌的天然感受态，通过突变分析研究了 MopB 的功能。在两种不同的木质部难养菌菌株 Temecula 和毒力更强的 WM1-1 中构建了 mopB 基因缺失突变体。mopB 基因的缺失削弱了细胞间聚集、表面附着和两种菌株的生物膜形成。有趣的是，mopB 缺失完全消除了 twitching 运动。细菌细胞表面的电子显微镜显示，mopB 缺失消除了 IV 型和 I 型菌毛的形成，这可能是由于外膜的不稳定。在温室条件下，用烟草（Nicotiana tabacum）作为宿主时，两种 mopB 突变体的毒力都降低。这些结果表明，MopB 在生物膜形成和 twitching 运动中具有多种功能，对木质部难养菌的毒力很重要。
