Wednesday Aug 21 // Calmodulin-like proteins in plant counterdefense against viral RNA silencing suppressors
Dr. Kenji Nakahara, Lecturer
Pathogen-Plant Interactions Group, Research Faculty of Agriculture,
Hokkaido University, Sapporo, Hokkaido 060-8589, Japan
RNA silencing is one of major antiviral systems in plants and most plant viruses encode RNA silencing suppressors (RSS) to facilitate their infection of plants by inhibiting the plant’s endogenous antiviral RNA-silencing machinery. Previously, a tobacco calmodulin-like protein (CML), termed rgs-CaM, has been reported to interact with HC-Pro and 2b, which are RSSs encoded by members of the genus Potyvirus and Cucumovirus, respectively. We have shown that the tobacco CML counteractively functions as an antiviral defense factor to direct degradation of its interacting RSS proteins via autophagy. Further studies suggest that the rgs-CaM-mediated counterdefense against RSSs involves salicylic acid signaling. Plants encode dozens of CMLs (50 and 32 CMLs in Arabidopsis and rice, respectively). Several CMLs of tobacco and other plants are similar to rgs-CaM in their amino acid sequences, suggesting possible binding to viral RSSs and involvement with antiviral defense. We have been investigating whether Arabidopsis CML orthologs of rgs-CaM may be involved in plant/virus interaction and I will present data from research in Japan and recent collaborative work in the Snedden lab here at Queen’s.