Luisa Fernanda Castiblanco, Juliana Gil, Alejandro Rojas, Daniela Osorio, Sonia Gutiérrez, Alejandra Muñoz Bodnar, Alvaro L. Perez-Quintero, Ralf Koebnik, Boris Szurek, Camilo López, Silvia Restrepo, Valérie Verdier, and Adriana J. Bernal (2013)

TALE1 from Xanthomonas axonopodis pv. manihotis acts as a transcriptional activator in plant cells and is important for pathogenicity in cassava plants

Molecular Plant Pathology 14 (1) 84-95

Many plant-pathogenic bacteria suppress pathogen-associated molecular pattern (PAMP)-triggered immunity by injecting effector proteins into the host cytoplasm during infection through the type III secretion system (TTSS). This type III secretome plays an important role in bacterial pathogenicity in susceptible hosts. Xanthomonas axonopodis pv. manihotis (Xam), the causal agent of cassava bacterial blight, injects several effector proteins into the host cell, including TALE1_Xam. This protein is a member of the Transcriptional Activator-Like effector (TALE) protein family, formerly known as the AvrBs3/PthA family. TALE1_Xam has 13.5 tandem repeats of 34 amino acids each, as well as two nuclear localization signals and an acidic activation domain at the C-terminus. In this work, we demonstrate the importance of TALE1_Xam in the pathogenicity of Xam. We use versions of the gene that lack different domains in the protein in structure-function studies to show that the eukaryotic domains at the 3' end are critical for pathogenicity. In addition, we demonstrate that, similar to the characterized TALE proteins from other Xanthomonas species, TALE1_Xam acts as a transcriptional activator in plant cells. This is the first report of the identification of a TALE in Xam, and contributes to our understanding of the pathogenicity mechanisms employed by this bacterium to colonize and cause disease in cassava.

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