Several Nucleoporins And R Proteins Are Essential For BAK1 And BKK1-Mediated Cell-Death Control In Arabidopsis Thaliana

Arabidopsis BAK1 and its paralog BKK1 were found to regulate BR-independent and salicylic acid(SA)-dependent spontaneous cell-death pathways.A double null mutant bak1-4 bkkl-1 displays a lethality phenotype about one week after germination even when grown under sterile conditions.To date,molecular mechanisms of the cell-death signal transduction remain unclear.bak1-3 bkk1-1 double mutant,however,can express a reduced amount of wild-type BAK1 mRNA and shows a much reduced cell-death phenotype than bak1-4 bkk1-1.A genetic suppressor named sbbl-1 was identified via genetic modifier screen for the weak mutant.Genetic analyses show that the cell-death suppression was caused by a loss-of-function mutant of SBB1 which encodes a nucleoporin(NUP)85-like protein belonging to the NUP107-160 subcomplex.Here we report that SBB1 is a novel regulator fundamental for BAK1 and BKKl-mediated cell-death signaling pathway,but not required for birl,bonl or mkk1-triggered cell death control.Our genetic evidence also demonstrated that members of NUP107-160 subcomplex and SBB1 associated DRH1 are essential for BAK1 and BKK1-mediated spontaneous cell death signaling pathway in Arabidopsis.Further,RBB1 family genes were identified playing important roles in modulating bakl bkk1-conferred cell death control by using an RNAi approach.