Centro APTA Citros Sylvio Moreira, Cordeirópolis, SP Brazil.
Genet Mol Biol. 2010 Jan;33(1):146-53. doi: 10.1590/S1415-47572009005000110. Epub 2010 Mar 1.
The Gram-negative bacterium Xanthomonas axonopodis pv. citri, the causal agent of citrus canker, is a major threat to the citrus industry worldwide. Although this is a leaf spot pathogen, it bears genes highly related to degradation of plant cell walls, which are typically found in plant pathogens that cause symptoms of tissue maceration. Little is known on Xac capacity to cause disease and hydrolyze cellulose. We investigated the contribution of various open reading frames on degradation of a cellulose compound by means of a global mutational assay to selectively screen for a defect in carboxymethyl cellulase (CMCase) secretion in X. axonopodis pv. citri. Screening on CMC agar revealed one mutant clone defective in extracellular glycanase activity, out of nearly 3,000 clones. The insertion was located in the xpsD gene, a component of the type II secretion system (T2SS) showing an influence in the ability of Xac to colonize tissues and hydrolyze cellulose. In summary, these data show for the first time, that X. axonopodis pv. citri is capable of hydrolyzing cellulose in a T2SS-dependent process. Furthermore, it was demonstrated that the ability to degrade cellulose contributes to the infection process as a whole.
革兰氏阴性细菌黄单胞菌属柑橘溃疡亚种，是柑橘溃疡病的病原体，是对全球柑橘产业的主要威胁。尽管这是一种叶斑病病原体，但它具有与植物细胞壁降解高度相关的基因，这些基因通常存在于导致组织糜化症状的植物病原体中。关于 Xac 引起疾病和水解纤维素的能力知之甚少。我们通过全局突变分析研究了各种开放阅读框在降解纤维素化合物中的作用，以便选择性筛选柑橘溃疡亚种羧甲基纤维素酶（CMCase）分泌缺陷。在 CMC 琼脂上筛选显示，在近 3000 个克隆中，有一个突变体克隆在外切糖苷酶活性方面存在缺陷。该插入位于 xpsD 基因中，该基因是 II 型分泌系统（T2SS）的一个组成部分，该系统显示出对 Xac 定植组织和水解纤维素能力的影响。总之，这些数据首次表明，柑橘溃疡亚种黄单胞菌属能够在 T2SS 依赖的过程中水解纤维素。此外，还证明了纤维素的降解能力有助于整个感染过程。
