Glyceraldehyde-3-phosphate dehydrogenase of Xanthomonas campestris pv. campestris is required for extracellular polysaccharide production and full virulence

• Published in: Microbiology (Society for General Microbiology) 2009-05, Vol.155 (5), p.1602-1612
• Main Authors: Lu, Guang-Tao, Xie, Jia-Ri, Chen, Lei, Hu, Jiang-Ru, An, Shi-Qi, Su, Hui-Zhao, Feng, Jia-Xun, He, Yong-Qiang, Jiang, Bo-Le, Tang, Dong-Jie, Tang, Ji-Liang
• Format: Article
• Language: English
• Subjects: Adenosine Triphosphate - metabolism; Bacterial Proteins - genetics; Bacterial Proteins - metabolism; Bacteriology; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Bacterial; Gene Expression Regulation, Enzymologic; Glyceraldehyde-3-Phosphate Dehydrogenases - genetics; Glyceraldehyde-3-Phosphate Dehydrogenases - metabolism; Microbiology; Miscellaneous; Plant Diseases - microbiology; Polysaccharides, Bacterial - biosynthesis; Raphanus - microbiology; Virulence; Xanthomonas campestris; Xanthomonas campestris - enzymology; Xanthomonas campestris - genetics; Xanthomonas campestris - pathogenicity
• ISSN: 1350-0872; 1465-2080
• DOI: 10.1099/mic.0.023762-0

Guangxi Key Laboratory of Subtropical Bioresources Conservation and Utilization, The Key Laboratory of Ministry of Education for Microbial and Plant Genetic Engineering, and College of Life Science and Technology, Guangxi University, 100 Daxue Road, Nanning, Guangxi 530004, PR China Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) plays an important role in glucose catabolism, converting glyceraldehyde 3-phosphates to 1,3-bisphosphoglycerates. Open reading frame (ORF) XC_0972 in the genome of Xanthomonas campestris pv. campestris ( Xcc ) strain 8004 is the only ORF in this strain annotated to encode a GAPDH. In this work, we have demonstrated genetically that this ORF encodes a unique GAPDH in Xcc strain 8004, which seems to be constitutively expressed. A GAPDH-deficient mutant could still grow in medium with glucose or other sugars as the sole carbon source, and no phosphofructokinase activity was detectable in strain 8004. These facts suggest that Xcc may employ the Entner–Doudoroff pathway, but not glycolysis, to utilize glucose. The mutant could not utilize pyruvate as sole carbon source, whereas the wild-type could, implying that the GAPDH of Xcc is involved in gluconeogenesis. Furthermore, inactivation of the Xcc GAPDH resulted in impairment of bacterial growth and virulence in the host plant, and reduction of intracellular ATP and extracellular polysaccharide (EPS). This reveals that GAPDH is required for EPS production and full pathogenicity of Xcc . Correspondence Ji-Liang Tang jltang{at}gxu.edu.cn Abbreviations: ED, Entner–Doudoroff; EPS, extracellular polysaccharide; GAP, glyceraldehyde 3-phosphate; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GUS, β -glucuronidase; Kan, kanamycin; RACE, rapid amplification of cDNA ends; Rif, rifampicin; TCA, tricarboxylic acid; Tet, tetracycline; Xcc , Xanthomonas campestris pv. campestris A supplementary table showing bacterial strains and plasmids used in this work is available with the online version of this paper.