Xia Tian, Li Yanjiao, Sun Dongling, Zhuo Tao, Fan Xiaojing, Zou Huasong
Fujian Province Key Laboratory of Plant Virology, College of Plant Protection, Fujian Agriculture and Forestry University, Fuzhou 350002, PR China.
PLoS One. 2016 Mar 7;11(3):e0151017. doi: 10.1371/journal.pone.0151017. eCollection 2016.
Xanthomonas citri subsp. citri causes citrus canker disease, which is characterized by the formation of water-soaked lesions, white or yellow spongy pustules and brown corky canker. In this work, we report the contribution of extracellular endoglucanase to canker development during infection. The ectopic expression of nine putative cellulases in Escherichia coli indicated that two endoglucanases, BglC3 and EngXCA, show carboxymethyl cellulase activity. Both bglC3 and engXCA genes were transcribed in X. citri subsp. citri, however, only BglC3 protein was detected outside the cell in western blot analysis. The deletion of bglC3 gene resulted in complete loss of extracellular carboxymethyl cellulase activity and delayed the onset of canker symptoms in both infiltration- and wound-inoculation assays. When growing in plant tissue, the cell density of bglC3 mutant was lower than that of the wild type. Our data demonstrated that BglC3 is an extracellular endoglucanase required for the full virulence of X. citri subsp. citri.
柑橘溃疡病菌引起柑橘溃疡病，其特征是形成水渍状病斑、白色或黄色海绵状脓疱以及褐色木栓化溃疡。在本研究中，我们报道了细胞外内切葡聚糖酶在感染过程中对溃疡病发展的作用。在大肠杆菌中对9种假定的纤维素酶进行异位表达，结果表明两种内切葡聚糖酶BglC3和EngXCA具有羧甲基纤维素酶活性。bglC3和engXCA基因在柑橘溃疡病菌中均有转录，然而，在蛋白质免疫印迹分析中仅在细胞外检测到BglC3蛋白。bglC3基因的缺失导致细胞外羧甲基纤维素酶活性完全丧失，并且在浸润接种和创伤接种试验中均延迟了溃疡病症状的出现。在植物组织中生长时，bglC3突变体的细胞密度低于野生型。我们的数据表明，BglC3是柑橘溃疡病菌完全致病力所需的一种细胞外内切葡聚糖酶。
