Virus-Plant Protein Interactions: The Importance of the Potato leafroll virus Readthrough Protein

Abstract

Potato leafroll virus’ (PLRV’s) C-terminal domain of the readthrough protein (RTP) is known to be involved with active retention of the virus in plant phloem. In this investigative study we used a combined proteomics and molecular virology approach to determine the identity and function of those plant proteins that are interacting with the readthrough domain of the RTP. Using a novel, on-plate co-immunoprecipitation method, we compared those plant proteins co-immunoprecipitating with the wild type form of PLRV with those that co-immunoprecipitate with a mutant form of the virus lacking the readthrough domain using N. benthamiana as a model system. Controls were thoroughly characterized to identify proteins that were non-specifically interacting with virus. Our research yielded four candidate proteins that appear to interact with the readthrough domain of the RTP and hence, are likely involved with phloem retention. The candidate proteins are as follows: 14-3-3 protein (AT1G78300.1), probable 26S proteasome non-ATPase regulatory subunit 3, membrane steroid-binding protein 2, and elicitor-inducible protein EIG J7. These four proteins were detected in the WT PLRV infected N. benthamiana as having 2.5-fold or greater enrichment as judged by spectral counts over a mutant that lacked the readthrough domain (ΔRTP) or control N. benthamiana tissue, and were also found in the host potato system with 2.5-fold or greater enrichment in WT PLRV infected potato as compared to healthy potato. These candidate proteins will be the focus of future validation studies to determine the function of these plant proteins in PLRV infection.