Interplay between potato virus X and RNA granules in Nicotiana benthamiana.

Cytoplasmic RNA granules consist of microscopic agglomerates of mRNAs and proteins and occur when the translation is reversibly and temporally halted (stress granules, SGs) or mRNAs are targeted for decapping (processing bodies, PBs). The induction of RNA granules formation by virus infection is a common feature of mammalian cells. However, plant-virus systems still remain poorly characterized. In this work, the SG marker AtUBP1b was expressed in Nicotiana benthamiana plants to decipher how the virus infection of plant cells affects SG dynamics. We found that the hypoxia-induced SG assembly was substantially inhibited in Potato virus X (PVX)-infected cells. Furthermore, we determined that the expression of PVX movement protein TGBp1 by itself, mimics the inhibitory effect of PVX on SG formation under hypoxia. Importantly, overexpression of AtUBP1b showed inhibition of the PVX spreading, whereas the overexpression of the dominant negative AtUBP1brrm enhanced PVX spreding, indicating that AtUBP1b negatively affects PVX infection. Notably, PVX infection did not inhibit the formation of processing bodies (PBs), indicating PVX has distinct effects depending on the type of RNA granule. Our results suggest that SG inhibition could be part of the virus strategy to infect the plant.