AsnB, regulated by diffusible signal factor and global regulator Clp, is involved in aspartate metabolism, resistance to oxidative stress and virulence in Xanthomonas oryzae pv. oryzicola. (16th November 2012)

• Record Type: Journal Article
• Authors: Qian, Guoliang; Liu, Chunhui; Wu, Guichun; Yin, Fangqun; Zhao, Yancun; Zhou, Yijing; Zhang, Yanbing; Song, Zhiwei; Fan, Jiaqin; Hu, Baishi; Liu, Fengquan
• Is Part Of: Molecular plant pathology. Volume 14:Number 2(2013:Feb.)
• Page Start: 145
• Page End: 157
• Publication Date: 2012-11-16
• Subjects: Plant diseases -- Molecular aspects -- Periodicals; Plant-pathogen relationships -- Molecular aspects -- Periodicals; 571.936
• DOI: 10.1111/j.1364-3703.2012.00838.x
• Languages: English
• ISSNs: 1464-6722

Abstract

<abstract abstract-type="main"> <title>Summary</title> <p> <italic>Xanthomonas oryzae</italic> pv. <italic>oryzicola</italic> (<italic>Xoc</italic>) causes bacterial leaf streak in rice, which is a destructive disease worldwide. <italic>Xoc</italic> virulence factors are regulated by diffusible signal factor (DSF) and the global regulator Clp. In this study, we have demonstrated that <italic>asnB</italic> (<italic>XOC_3054</italic>), encoding an asparagine synthetase, is a novel virulence‐related gene regulated by both DSF and Clp in <italic>Xoc</italic>. A sequence analysis revealed that AsnB is highly conserved in <italic>Xanthomonas</italic>. An <italic>asnB</italic> mutation in <italic>Xoc</italic> dramatically impaired pathogen virulence and growth rate in host rice, but did not affect the ability to trigger the hypersensitive response in nonhost (plant) tobacco. Compared with the wild‐type strain, the <italic>asnB</italic> deletion mutant was unable to grow in basic MMX (–) medium (a minimal medium without ammonium sulphate as the nitrogen source) with or without 10 tested nitrogen sources, except asparagine. The disruption of <italic>asnB</italic> impaired pathogen resistance to oxidative stress and reduced the transcriptional expression of <italic>oxyR</italic>, <italic>katA</italic> and <italic>katG</italic>, which encode three important proteins responsible for hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>) sensing and detoxification in <italic>Xanthomonas</italic> in the presence of H<sub>2</sub>O<sub>2</sub>, and nine important known <italic>Xoc</italic> virulence‐related genes in plant cell‐mimicking medium. Furthermore, the <italic>asnB</italic> mutation did not affect extracellular protease activity, extracellular polysaccharide production, motility or chemotaxis. Taken together, our results demonstrate the role of <italic>asnB</italic> in <italic>Xanthomonas</italic> for the first time.</p> </abstract>