Extracellular diadenosine tetraphosphate (Ap4A) is recognized by the plasma membrane purinoreceptor P2K1/DORN1 and closes stomata inArabidopsis thaliana

Abstract

SummaryDinucleoside polyphosphates (NpnNs) are considered novel signalling molecules involved in the induction of plant defence mechanisms. However, the NpnNs signal recognition and transduction are still enigmatic. Here we report, for the first time, that diadenosine tetraphosphate (Ap4A) is recognized by theArabidopsis thalianapurinoreceptor P2K1/DORN1 (Does Not Respond to Nucleotides 1) and causes stomatal closure.Extracellular Ap4A- and dicytidine tetraphosphate (Cp4C)-induced stomatal closure was observed using a microscope. Reactive oxygen species (ROS) accumulation was determined by staining with nitroblue tetrazolium (NBT) and 3,3ʹ-diaminobenzidine tetrahydrochloride (DAB). Transcriptional changes were determined by quantitative real-time PCR. Wild-type Col-0 and thedorn1-3 A. thalianaknockout mutant were used.Examination of the leaf epidermisdorn1-3mutant provided evidence that P2K1/DORN1 recognizes extracellular Ap4A but not Cp4C. ROS are involved in signal transduction caused by Ap4A and Cp4C, leading to stomatal closure. Ap4A induced and Cp4C suppressed the transcriptional response in wild-type plants. Moreover, indorn1-3leaves, the effect of Ap4A on gene expression was impaired.Our research demonstrated, for the first time, that P2K1/DORN1 is a plant purinoreceptor for Ap4A. This interaction leads to changes in the transcription of signalling hubs in signal transduction pathways.