Characterization of the interaction between the Beet Necrotic Yellow Vein Virus pathogenicity factor P25 and an Auxin/indole-3-acetic acid protein from sugar beet
S. LIEBE (1), H. Thiel (2), D. Gilmer (3), M. Varrelmann (2) (1) Institute of Sugar Beet Research, Germany; (2) Institute of Sugar Beet Research, Germany; (3) Institut de Biologie Moléculaire des Plantes, France

Auxin/indole-3-acetic acid (Aux/IAA) proteins are negative regulators of auxin transcription factors (ARF). This interaction is crucial for the auxin signaling pathway as it determines the expression of auxin responsive genes. Viral proteins are able to target plant Aux/IAA proteins and to change their cellular localization. This enables plant viruses to alter the expression activity of auxin response genes and to induce symptom development as demonstrated for the Tobacco Mosaic Virus. In our previous work, an Aux/IAA protein from sugar beet was identified in YTH as an putative interaction partner of the Beet Necrotic Yellow Vein Virus (BNYVV) main pathogenicity factor P25 that is responsible for symptom development and yield loss. As auxin is involved in lateral root development and BNYVV causes development of massive lateral root proliferation, the hypothesis was raised that P25?Aux/IAA interaction might be the basis for the virus induced morphological changes. The P25-Aux/IAA interaction was confirmed in vitro by applying GST-pull down assay. Both proteins interacted in planta as demonstrated by bimolecular fluorescence complementation assay. Subcellular localization in N. benthamiana showed that P25 localizes to both cytoplasma and nucleus whereas the Aux/IAA protein localizes exclusively to the nucleus. Transient expression of both proteins revealed that the Aux/IAA protein was re-localized to the cytoplasm in the presence of P25. This re?localization was not observed when a P25 mutant defective in nuclear localization (P25ΔNLS) was co-expressed. The fluorescence was restricted to the nucleus confirming that the P25ΔNLS was actively transported to the nucleus by Aux/IAA. The results provide for the first time evidence that the main BNYVV pathogenicity factor P25 interacts with sugar beet Aux/IAA. It is suspected that this interaction alter the expression activity of auxin response genes leading to extensive lateral root development.

Abstract Number: P16-456
Session Type: Poster