EcpA, an extracellular protease, is a specific virulence factor required by Xanthomonas oryzae pv. oryzicola but not by X. oryzae pv. oryzae in rice.
Previously, 12 protease-deficient mutants of the Xanthomonas oryzae pv. oryzicola (Xoc) RS105 strain were recovered from a Tn5-tagged mutant library. In the current study, the Tn5 insertion site in each mutant was mapped. Mutations in genes encoding components of the type II secretion apparatus, cAMP regulatory protein, integral membrane protease subunit, S-adenosylmethionine decarboxylase proenzyme and extracellular protease (ecpA(Xoc)) either partially or completely abolished extracellular protease activity (ECPA) and reduced virulence in rice. Transcription of ecpA(Xoc) was induced in planta in all the mutants except RΔecpA. Complementation of RΔecpA with ecpA(Xoc) in trans restored ECPA, virulence and bacterial growth in planta. Purified EcpA(Xoc) induced chlorosis- and necrosis-like symptoms similar to those induced by the pathogen when injected into rice leaves. Heterologous expression of ecpA(Xoc) conferred ECPA upon the vascular bacterium X. oryzae pv. oryzae (Xoo) and upon non-pathogenic Escherichia coli. Genetic analysis demonstrated that the C-terminal residues of EcpA in Xoo PXO99(A) and Xoc RS105 are different, and a frame shift in ecpA(Xoo) may explain the absence of EcpA activity in Xoo. Collectively, these results suggest that EcpA(Xoc) is a tissue-specific virulence factor for Xoc but not Xoo, although the two pathovars are closely related bacterial pathogens of rice.
School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, PR China.
Hua-Song
HS
Zou
School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, PR China.
Xue
X
Song
School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, PR China.
Li-Fang
LF
Zou
Department of Plant Pathology, Nanjing Agricultural University, Key Laboratory of Monitoring and Management for Plant Diseases and Insects, Ministry of Agriculture of China, Nanjing 210095, PR China.
Liang
L
Yuan
School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, PR China.
Yu-Rong
YR
Li
Department of Plant Pathology, Nanjing Agricultural University, Key Laboratory of Monitoring and Management for Plant Diseases and Insects, Ministry of Agriculture of China, Nanjing 210095, PR China.
Wei
W
Guo
Department of Plant Pathology, Nanjing Agricultural University, Key Laboratory of Monitoring and Management for Plant Diseases and Insects, Ministry of Agriculture of China, Nanjing 210095, PR China.
Yi-Zhou
YZ
Che
Department of Plant Pathology, Nanjing Agricultural University, Key Laboratory of Monitoring and Management for Plant Diseases and Insects, Ministry of Agriculture of China, Nanjing 210095, PR China.
Wen-Xiang
WX
Zhao
Horticultural Research Laboratory, Agricultural Research Service, USDA, Fort Pierce, FL 34945, USA.
Yong-Ping
YP
Duan
Department of Plant Pathology, Nanjing Agricultural University, Key Laboratory of Monitoring and Management for Plant Diseases and Insects, Ministry of Agriculture of China, Nanjing 210095, PR China.|School of Agriculture and Biology, Shanghai Jiao Tong University, Shanghai 200240, PR China.
Gong-You
GY
Chen
D004251:DNA Transposable Elements; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity; D020869:Gene Expression Profiling; D005816:Genetic Complementation Test; D016254:Mutagenesis, Insertional; D012275:Oryza / Q000382:microbiology*; D010447:Peptide Hydrolases / Q000235:genetics* / Q000378:metabolism*; D010935:Plant Diseases / Q000382:microbiology*; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism; D014974:Xanthomonas / Q000201:enzymology* / Q000472:pathogenicity*
D004251:DNA Transposable Elements; D037521:Virulence Factors; D010447:Peptide Hydrolases