A Functional Screen for the Type III (Hrp) Secretome of the Plant Pathogen Pseudomonas syringae

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Science  01 Mar 2002:
Vol. 295, Issue 5560, pp. 1722-1726
DOI: 10.1126/science.295.5560.1722

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Type III secreted “effector” proteins of bacterial pathogens play central roles in virulence, yet are notoriously difficult to identify. We used an in vivo genetic screen to identify 13 effectors secreted by the type III apparatus (called Hrp, for “hypersensitive response and pathogenicity”) of the plant pathogenPseudomonas syringae. Although sharing little overall homology, the amino-terminal regions of these effectors had strikingly similar amino acid compositions. This feature facilitated the bioinformatic prediction of 38 P. syringae effectors, including 15 previously unknown proteins. The secretion of two of these putative effectors was shown to be type III–dependent. Effectors showed high interstrain variation, supporting a role for some effectors in adaptation to different hosts.

  • * These authors contributed equally to this work.

  • To whom correspondence should be addressed. E-mail: guttman{at}

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