NIa-pro of Papaya ringspot virus interacts with papaya methionine sulfoxide reductase B1

A chloroplast-localized papaya methionine sulfoxide reductase B1 (PaMsrB1) interacting with Papaya ringspot virus (PRSV) NIa-Pro was identified using a Sos recruitment two-hybrid system (SRS). SRS analysis of several deletion mutants of PRSV NIa-Pro and PaMsrB1 demonstrated that the C-terminal (residues 133–239) fragment of PRSV NIa-Pro and residues 112–175 of PaMsrB1 were necessary for this interaction between PRSV NIa-Pro and PaMsrB1. MsrB1 can repair Met-oxidized proteins damaged by reactive oxygen species (ROS). We confirmed that PRSV infection leads to ROS accumulation and a slight upregulation of level PaMsrB1 mRNA in papaya. This interaction between PaMsrB1 with PRSV NIa-Pro may disturb the import of PaMsrB1 into the chloroplasts. These results suggest that this specific interaction could interfere with PaMsrB1 into the chloroplasts to scavenge ROS caused by PRSV infection. This may be a novel mechanism of PRSV towards the host defense.

► A chloroplast-localized PaMsrB1 interacting with PRSV NIa-Pro was identified.
► This interaction could disturb PaMsrB1 into the chloroplasts to scavenge ROS.
► This interaction may be involved in a novel mechanism of PRSV toward host defense.