Abstract
Plants recognize pathogen infection and induce rapid and strong defense responses including a localized cell death called hyper sensitive response. This defense system is controlled by resistance (R) proteins that recognize, directly or indirectly, pathogen effector molecules. Genetic approaches have led to the identification of several components of the R-protein triggered pathway. Among those identified, RAR1, HSP90 and SGT1 are required for resistance mediated by multiple R proteins recognizing viral, bacterial, oomycete or fungal pathogens. RAR1 and SGT1 interact with each other and with HSP90. The CS domain of SGT1, which binds both RAR1 and HSP90, has structural similarity to P23, a co-chaperon of HSP90. Silencing of RAR1, SGT1 or HSP90 in Nicotiana benthaminana plants resulted in reduction of R-protein levels. These results may suggest that the RAR1-SGT1-HSP90 complex works for stabilizing R proteins as a chaperon complex. The function of RAR1-SGT1-HSP90 complex will be discussed.
