Tight regulation of plant immune responses bycombining promoter and suicide exon elements

Abstract

Effector-triggered immunity (ETI) is activated whenplant disease resistance (R) proteins recognize thepresence of pathogen effector proteins deliveredinto host cells. The ETI response generally encompassesa defensive 'hypersensitive response' (HR) that involves programmed cell death at the site of pathogen recognition. While many R protein and effectorprotein pairs are known to trigger HR, othercomponents of the ETI signaling pathway remainelusive. Effector genes regulated by inducible promoterscause background HR due to leaky proteinexpression, preventing the generation of relevanttransgenic plant lines. By employing the HyP5SMsuicide exon, we have developed a strategy totightly regulate effector proteins such that HR ischemically inducible and non-leaky. This alternativesplicing-based gene regulation system was shownto successfully control Bs2/AvrBs2-dependent andRPP1/ATR1-51-dependent HR in Nicotiana benthamianaand Nicotiana tabacum, respectively. It wasalso used to generate viable and healthy transgenicArabidopsis thaliana plants that inducibly initiate HR.Beyond enabling studies on the ETI pathway, our regulatorystrategy is generally applicable to reduce oreliminate undesired background expression of transgene.