Leaf and tuber treatments with PAMPs trigger organ-specific responses in potato

Organ-specificity of plant defence is an under-represented axis of research in plant biology. However, recent publications point out the importance of this concept in plant-pathogen interactions. Indeed, assuming the resistance status of a whole plant against a given pathogen following studies conducted on a single organ might lead to erroneous conclusions. This study aims at understanding the extent of potato (Solanum tuberosum) organ-specific defence mechanisms after leaf and tuber treatments with pathogen-associated molecular patterns (PAMPs). Our results show that potato leaves and tubers activate contrasting defence responses, in terms of production of reactive oxygen species (ROS) and activation of defence-related genes, following treatments with the Phytophthora PAMP Pep-25 or the bacterial PAMP flg22. Interestingly, flg22 induced ROS production in both leaves and tubers, indicating that this peptide is recognized in these organs. By contrast, ROS production was induced in the leaf but not in the tuber after Pep-25 treatment. Analysis of changes in expression of defence-related genes showed that at least six genes exhibited organ-specific expression patterns. In addition to those early responses, inhibition of potato seedling growth was also found to affect both the aboveground and belowground organs following treatment with Pep-25 and with flg22. Taken together, these experiments will help further the investigation of potato defence against Phytophthora spp.