Arabidopsis CPR5 regulates ethylene signaling via interacting with ETR1 N-terminus and controlling mRNAs nucleocytoplasmic transport

ETR1 is the major ethylene receptor in Arabidopsis thaliana. Previous studies showed that RTE1 and CPR5 can bind to ETR1 and play regulatory roles in ethylene signaling. RTE1 has been suggested to promote ETR1 signal transduction by influencing the conformation of ETR1, but little is known about the mechanism of CPR5 on the regulation of ETR1 signaling. In this study, we showed that both CPR5 and RTE1 could interact with the N-terminal transmembrane domains of ETR1, and CPR5 needs at least three transmembrane domains of ETR1 while RTE1 needs only two for the binding. As CPR5 has also been shown to be localized in the nuclear membrane and might act as a nucleoporin, we analyzed the effects of CPR5 on the nucleocytoplasmic transport of ethylene-related mRNAs using poly(A)-mRNA in situ hybridization and real-time quantitative PCR (qPCR), and the results indicated that CPR5 could selectively regulate the nucleocytoplasmic transport of mRNAs in ethylene signaling pathway. In contrast, the nucleoporin mutants (nup160, nup96-1 and nup96-2) dramatically accumulated all the examined mRNAs in the nucleus. In conclusion, the present study provides evidence demonstrating that CPR5 regulates ethylene signaling through interacting with the ETR1 receptor and controlling the mRNAs nucleocytoplasmic transport in ethylene signaling pathway.