Role of unfolded protein response in plant virus infection.

A new study of Potato virus X (PVX) revealed that a viral movement protein, named TGBp3, triggers the unfolded protein response (UPR) which monitors accumulation of aberrant proteins the endoplasmic reticulum (ER) and targets them for degradation. The PVX TGBp3 resides in ER and activates bZIP60, a transcription factor involved in the UPR pathway. Knockdown of bZIP60 hampers virus infection in protoplasts and whole plants. Preliminary evidence indicates that UPR regulates cellular cytotoxicity that could otherwise lead to cell death if the PVX TGBp3 reaches high levels in the ER. SKP1 expression appears to be linked to bZIP60 and is a component of the SCF-complex mediating proteasomal degradation of cellular substrates. SKP1 expression is induced by PVX TGBp3 and plays a role in regulating PVX spread in whole plants. We propose that SKP1 might be linked to TGBp1-mediated degradation of AGO1.