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The Tobacco mosaic virus Replicase Protein Disrupts the Localization and Function of Interacting Aux/IAA Proteins

August 2006 , Volume 19 , Number  8
Pages  864 - 873

Meenu S. Padmanabhan , 1 Haiymanot Shiferaw , 2 and James N. Culver 1 , 2

1Department of Cell Biology and Molecular Genetics, University of Maryland, and 2Center for Biosystems Research, University of Maryland Biotechnology Institute, College Park, MD 20742, U.S.A.

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Accepted 26 March 2006.

Previously, we identified a correlation between the interaction of the Tobacco mosaic virus (TMV) 126/183-kDa replicase with the auxin response regulator indole acetic acid (IAA)26/PAP1 and the development of disease symptoms. In this study, the TMV replicase protein is shown to colocalize with IAA26 in the cytoplasm and prevent its accumulation within the nucleus. Furthermore, two additional auxin (Aux)/IAA family members, IAA27 and IAA18, were found to interact with the TMV replicase and displayed alterations in their cellular localization or accumulation that corresponded with their ability to interact with the TMV replicase. In contrast, the localization and accumulation of noninteracting Aux/IAA proteins were unaffected by the presence of the viral replicase. To investigate the effects of the replicase interaction on Aux/IAA function, transgenic plants expressing a proteolysis-resistant IAA26-P108H-green fluorescent protein (GFP) protein were created. Transgenic plants accumulating IAA26-P108H-GFP displayed an abnormal developmental phenotype that included severe stunting and leaf epinasty. However, TMV infection blocked the nuclear localization of IAA26-P108H-GFP and attenuated the developmental phenotype displayed by the transgenic plants. Combined, these findings suggest that TMV-induced disease symptoms can be attributed, in part, to the ability of the viral replicase protein to disrupt the localization and subsequent function of interacting Aux/IAA proteins.

Additional keywords: subcellular localization, virus disease.

© 2006 The American Phytopathological Society