title: Secretome analysis of rice suspension-cultured cells infected by Xanthomonas oryzae pv.oryza (Xoo).
abstract: BACKGROUND
  Rice bacterial blight (BB) caused by Xanthomonas oryzae pv.oryzae (Xoo) is one of the most devastating bacterial diseases in rice-growing regions worldwide. The rice-Xoo interaction is a classical model for studying the interaction between plants and pathogens. Secreted proteins play important roles in plant-bacterial interactions, but are poorly studied in the rice-Xoo system. Rice cv. Nipponbare is highly susceptible to Xoo. Here, we used two-dimensional difference gel electrophoresis (2D-DIGE) coupled with MALDI-TOF/TOF mass spectrometry (MS), to investigate secreted proteins in Nipponbare embryo cell suspension culture infected by Xoo.
  
  
  RESULTS
  A total of 32 protein spots changed significantly (p < 0.05) by more than 1.5 fold in gel intensity after Xoo inoculation, and were identified by MS. They represent protein products of 11 unique genes, seven from rice and four from Xoo. Of the rice proteins, six up-regulated proteins are involved in cell wall modification, the TCA cycle, glycolysis and redox, while a down-regulated protein, CHIT16, is involved in plant defense. Quantitative Real-Time PCR showed that transcript levels were not correlated with secreted protein levels. Of the Xoo proteins, three of them were possibly located in the extracellular space as shown by transient expression assays in rice protoplasts. Two of the Xoo proteins were previously reported to be likely involved in pathogenicity, and the third gene, Xoo3654, is likely a negative regulator of Xoo virulence as its overexpression reduced Xoo pathogenicity in our study.
  
  
  CONCLUSIONS
  Among the secreted proteins that responded to Xoo inoculation, we identified rice proteins involved in cell defense and Xoo proteins involved in pathogenicity. Our study also showed that Xoo3654 (X2) protein is likely a novel negative regulator of Xoo virulence. These results not only help us better understand the interaction between susceptible rice and Xoo, but also serve as a reference for studying the interaction between other plants and their pathogens.
authors.affiliation: College of Agriculture and Biotechnology, Zhejiang University, Hangzhou, China ; State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, MOA Key Laboratory of Biotechnology in Plant Protection, Zhejiang Provincial Key Laboratory of Plant Virology, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Science, Hangzhou, 310021 China.
authors.forename: Xian
authors.initials: X
authors.lastname: Chen
authors.affiliation: State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, MOA Key Laboratory of Biotechnology in Plant Protection, Zhejiang Provincial Key Laboratory of Plant Virology, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Science, Hangzhou, 310021 China.
authors.forename: Zhiping
authors.initials: Z
authors.lastname: Deng
authors.affiliation: State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, MOA Key Laboratory of Biotechnology in Plant Protection, Zhejiang Provincial Key Laboratory of Plant Virology, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Science, Hangzhou, 310021 China.
authors.forename: Chulang
authors.initials: C
authors.lastname: Yu
authors.affiliation: State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, MOA Key Laboratory of Biotechnology in Plant Protection, Zhejiang Provincial Key Laboratory of Plant Virology, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Science, Hangzhou, 310021 China.
authors.forename: Chengqi
authors.initials: C
authors.lastname: Yan
authors.affiliation: State Key Laboratory Breeding Base for Zhejiang Sustainable Pest and Disease Control, MOA Key Laboratory of Biotechnology in Plant Protection, Zhejiang Provincial Key Laboratory of Plant Virology, Institute of Virology and Biotechnology, Zhejiang Academy of Agricultural Science, Hangzhou, 310021 China.
authors.forename: Jianping
authors.initials: J
authors.lastname: Chen
keywords: 2-D DIGE; Bacterial blight; MS; Secretome; Xoo3654
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