ARS | Publication request: CRYPTOCHROME 2 and PHOTOTROPIN 2 regulate resistance protein mediated viral 2 defense by negatively regulating a E3 ubiquitin ligase

Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 1, 2010
Publication Date: July 27, 2010
Citation: Jeong, R., Chandra-Shekara, A.C., Barman, S., Navarre, D.A., Klessig, D., Kachroo, A., Kachroo, P. 2010. CRYPTOCHROME 2 and PHOTOTROPIN 2 regulate resistance protein mediated viral 2 defense by negatively regulating a E3 ubiquitin ligase. Proceedings of the National Academy of Sciences. 107(30):13538-43.

Interpretive Summary: Much remains to be learned about the mechanisms plants use to resist disease. Understanding how plants resist disease will allow the development of plants with superior disease resistance, that require less pesticide use and lead to greater sustainability and food security. This study describes a novel mechanism by which light regulates plant resistance to a virus through a complex interaction between photoreceptors and plant resistance genes involving proteasome-mediated degradation of the R-gene. R-genes are one of the most important mechansims involved in the resistance of plants to pathogens.

Technical Abstract: Light harvested by plants is essential for the survival of most life forms. This light perception ability requires the activities of proteins termed photoreceptors. We report a function for photoreceptors in mediating resistance (R) protein-derived plant defense. The blue-light photoreceptors, cryptochrome (CRY) 2 and phototropin (PHOT) 2, are required for the stability of the R protein HRT, and thereby resistance to Turnip Crinkle virus (TCV). Exposure to darkness or blue-light induces degradation of CRY2, and in turn HRT, resulting in susceptibility. Overexpression of HRT can compensate for the absence of PHOT2 but not CRY2. HRT does not directly associate with either CRY2 or PHOT2 but does bind the CRY2-/PHOT2-interacting E3 ubiquitin ligase, COP1. Application of the proteasome inhibitor, MG132, prevents blue-light-dependent degradation of HRT, consequently these plants show resistance to TCV under blue-light. We propose that CRY2/PHOT2 negatively regulate the proteasome-mediated degradation of HRT, likely via COP1, and blue-light relieves this repression resulting in HRT degradation.