The Plasma Membrane Purinoreceptor P2K1/DORN1 Is Essential in Stomatal Closure Evoked by Extracellular Diadenosine Tetraphosphate (Ap 4 A) in Arabidopsis thaliana .

Dinucleoside polyphosphates (Npn Ns) are considered novel signalling molecules involved in the induction of plant defence mechanisms. However, Npn N signal recognition and transduction are still enigmatic. Therefore, the aim of our research was the identification of the Npn N receptor and signal transduction pathways evoked by these nucleotides. Earlier, we proved that purine and pyrimidine Npn Ns differentially affect the phenylpropanoid pathway in Vitis vinifera suspension-cultured cells. Here, we report, for the first time, that both diadenosine tetraphosphate (Ap4 A) and dicytidine tetraphosphate (Cp4 C)-induced stomatal closure in Arabidopsis thaliana . Moreover, we showed that plasma membrane purinoreceptor P2K1/DORN1 (does not respond to nucleotide 1) is essential for Ap4 A-induced stomata movements but not for Cp4 C. Wild-type Col-0 and the dorn1-3 A. thaliana knockout mutant were used. Examination of the leaf epidermis dorn1-3 mutant provided evidence that P2K1/DORN1 is a part of the signal transduction pathway in stomatal closure evoked by extracellular Ap4 A but not by Cp4 C. Reactive oxygen species (ROS) are involved in signal transduction caused by Ap4 A and Cp4 C, leading to stomatal closure. Ap4 A induced and Cp4 C suppressed the transcriptional response in wild-type plants. Moreover, in dorn1-3 leaves, the effect of Ap4 A on gene expression was impaired. The interaction between P2K1/DORN1 and Ap4 A leads to changes in the transcription of signalling hubs in signal transduction pathways.