Assassination Tango: An NLR/NLR-ID immune receptors pair of rapeseed co-operates inside the nucleus to activate cell death

Abstract

Plant immunity relies on cell-surface receptors and intracellular NLR immune receptors. Some plant NLRs carry integrated domains (IDs) that that mimic authentic pathogens effector targets. We report here the identification in Brassica napus of the genetically linked NLR/NLR-ID pair, BnRPR1 and BnRPR2. The NLR-ID carries two ID fusions and their mode of action conforms to the proposed "integrated sensor/decoy" model. The two NLRs interact and the heterocomplex localizes in the plant-cell nucleus and nucleolus. However, the BnRPRs pair does not operate through a negative regulation as it was previously reported for other NLR-IDs. Cell death is induced only upon co-expression of the two proteins and it is dependent on the helper genes EDS1 and NRG1. Truncations of the IDs of BnRPR1 results in cytoplasmic localization and compromises cell death activation. Expression, using the native promoter in Nicotiana species, led to a conditional cell death induction. However, this was not the case for the transgenic Arabidopsis, where no cell death was observed. In summary, we describe a new pair of NLR-IDs with interesting features in relation to its regulation and the cell death activation.