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HopZ4 from Pseudomonas syringae, a Member of the HopZ Type III Effector Family from the YopJ Superfamily, Inhibits the Proteasome in Plants

July 2014 , Volume 27 , Number  7
Pages  611 - 623

Suayib Üstün,1,2 Patrick König,2 David S. Guttman,3,4 and Frederik Börnke1,2

1Leibniz-Institute for Vegetable and Ornamental Plants (IGZ), Theodor-Echtermeyer-Weg 1, 14979 Großbeeren, Germany; 2Friedrich-Alexander-University Erlangen-Nuremberg, Staudtstr. 5, 91058 Erlangen, Germany; 3Department of Cell and Systems Biology and 4Centre for the Analysis of Genome Evolution and Function, University of Toronto, Toronto, ON, Canada

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Accepted 28 February 2014.

The YopJ family of type III effector proteins (T3E) is one of the largest and most widely distributed families of effector proteins, whose members are highly diversified in virulence functions. In the present study, HopZ4, a member of the YopJ family of T3E from the cucumber pathogen Pseudomonas syringae pv. lachrymans is described. HopZ4 shares high sequence similarity with the Xanthomonas T3E XopJ, and a functional analysis suggests a conserved virulence function between these two T3E. As has previously been shown for XopJ, HopZ4 interacts with the proteasomal subunit RPT6 in yeast and in planta to inhibit proteasome activity during infection. The inhibitory effect on the proteasome is dependent on localization of HopZ4 to the plasma membrane as well as on an intact catalytic triad of the effector protein. Furthermore, HopZ4 is able to complement loss of XopJ in Xanthomonas spp., as it prevents precocious host cell death during a compatible Xanthomonas-pepper interaction. The data presented here suggest that different bacterial species employ inhibition of the proteasome as a virulence strategy by making use of conserved T3E from the YopJ family of bacterial effector proteins.

© 2014 The American Phytopathological Society