P-231 - An IDR-Containing Transcription Factor Interacts with PepMV TGB1 and Is a Component of Viral Replication Organelles

Pepino mosaic virus (PepMV; Potexvirus pepini) is responsible for worldwide epidemics in tomato crops, causing significant economic losses. In this study, we characterized the SlALOG-9/PepMV TGB1 interaction, firstly identified in a yeast two hybrid screening. SlALOG9 belongs to a tomato transcription factor family of 12 members, contains an ALOG domain and two intrinsically disorder regions (IDRs), and is presumably involved in floral development. CRISPR/Cas9-induced slalog-9 knockout tomato mutants showed significantly reduced viral titres, suggesting a proviral role for SlALOG-9 during PepMV infection. Transient expression of fluorescently tagged SlALOG-9 and TGB1 revealed that these proteins colocalize in the nuclei and relocate to viral replication organelles (VROs). SlALOG-9 is the only ALOG family member that interacts with TGB1 and relocates to VROs. Both SlALOG-9 IDRs were required for its relocalization, and replacing either with the corresponding IDR from its closest homolog prevented this process. The specific interaction between SlALOG-9 and TGB1 was further confirmed in the nuclei of infected cells by BiFC and FRET-FLIM. These findings suggest that PepMV TGB1 actively sequesters nuclear SlALOG-9 to VROs, likely promoting VRO stability through IDR-mediated protein interactions within these organelles. This work sheds light on the biological relevance of the TGB1 nuclear localization, contributing to a better understanding of host-virus interactions.