The p33 auxiliary replicase protein of Cucumber necrosis virus targets peroxisomes and infection induces de novo peroxisome formation from the endoplasmic reticulum.

Tombusviruses replicate on pre-existing organelles such as peroxisomes or mitochondria, the membranes of which become extensively reorganized into multivesicular bodies (MVBs) during the infection process. Cucumber necrosis virus (CNV) has previously been shown to replicate in association with peroxisomes in yeast. We show that CNV induces MVBs from peroxisomes in infected plants and that GFP-tagged p33 auxiliary replicase protein colocalizes with YFP(SKL), a peroxisomal marker. Most remarkably, the ER of CNV infected Nicotiana benthamiana 16C plants undergoes a dramatic reorganization producing numerous new peroxisome-like structures that associate with CNV p33, thus likely serving as a new site for viral RNA replication. We also show that plants agroinfiltrated with p33 develop CNV-like necrotic symptoms which are associated with increased levels of peroxide. Since peroxisomes are a site for peroxide catabolism, and peroxide is known to induce plant defense responses, we suggest that dysfunctional peroxisomes contribute to CNV induced necrosis.