Proteomic analysis of the proteins regulated by HrpB from the plant pathogenic bacterium Burkholderia glumae.
Plant pathogenic bacteria transfer effector proteins into plant cells via the hypersensitive response and pathogenicity (Hrp) type III protein secretion system (T3SS) during infection. The genes encoding the Hrp T3SS are expressed only under plant apoplast-mimicking conditions in an AraC-type transcriptional activator HrpB-dependent manner. To identify the proteins controlled by HrpB in Burkholderia glumae in vitro, we constitutively expressed hrpB and analyzed the proteins showing altered expression using 2-DE and ESI-MS/MS. Among 46 proteins exhibiting consistently altered expression, which were encoded by 34 different genes, 34 were secretory proteins and 12 were cytoplasmic. Twenty-eight of the secreted proteins showed increased accumulation, whereas the other six showed decreased accumulation. None of the HrpB-dependent proteins had significant homology to known T3SS-dependent proteins, except for HrpK from Pseudomonas syringae pv. syringae and two T3SS-associated cytoplasmic proteins from Ralstonia solanacearum. Twenty-one of the 34 genes had putative HrpB-binding sequences in their upstream regulatory regions. Secretion of all 34 extracellular proteins was independent of the Hrp T3SS, and 16 were secreted via a type II protein secretion system (T2SS). Mutants lacking the T2SS or Hrp T3SS produced toxoflavin but were less virulent to rice panicles, indicating the importance of these proteins in pathogenicity.
Department of Agricultural Biotechnology, Seoul National University, Seoul, Korea.
Yongsung
Y
Kang
Jinwoo
J
Kim
Suhyun
S
Kim
Hongsup
H
Kim
Jae Yun
JY
Lim
Minkyun
M
Kim
Jangyul
J
Kwak
Jae Sun
JS
Moon
Ingyu
I
Hwang
D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D019117:Burkholderia / Q000235:genetics* / Q000472:pathogenicity; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology; D015180:Electrophoresis, Gel, Two-Dimensional; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D008969:Molecular Sequence Data; D012275:Oryza / Q000382:microbiology; D010935:Plant Diseases / Q000382:microbiology*; D040901:Proteomics; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics; D014774:Virulence
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D015534:Trans-Activators