Spatial accumulation of salicylic acid is regulated by RBOHD in potato immunity against viruses

While activation of resistance (R) proteins has been intensively studied, the downstream signaling mechanisms leading to restriction of pathogen remain mostly unknown. We studied the immunity network response conditioned by the potato Ny-1 gene against potato virus Y. We analyzed the processes in the cell death zone and surrounding tissue on the biochemical and gene expression levels to reveal spatiotemporal regulation of immune response. We show that the transcriptional response in the cell death zone and surrounding tissue is dependent on salicylic acid (SA). For some genes, spatiotemporal regulation is completely lost in SA-deficient line, while the others show different response, indicating multiple connections between hormonal signaling modules. The induction of NADPH oxidase RBOHD expression occurs specifically on the lesion border during resistance response. In plants with silenced RBOHD, the functionality of resistance response is perturbed and virus spread is not arrested at the site of infection. RBOHD is required for spatial accumulation of SA, and conversely RBOHD is under transcriptional regulation of SA signaling. Using spatially resolved RNA-Seq, we also identified spatial regulation of an UDP-glucosyltransferase, another component in feedback activation of SA biosynthesis, thus deciphering a novel aspect of resistance signaling.