PROJECT SUMMARY

Potato spindle tuber viroid (PSTVd) is the most important subviral pathogen of potato (Solanum tuberosum L.). Due to its worldwide distribution and its capacity to cause disease in many important crop plants, PSTVd is one of the main constraints on food production. The molecular mechanisms by which viroids induce complex changes in host gene expression and metabolism are not fully understood. Current findings indicate that many signal transduction pathways involved in plant-viroid interactions are mediated by phytohormones. The main goal of this study is to analyze the dynamic of potato-PSTVd interaction, in order to obtain a more comprehensive view of phytohormone-mediated responses to PSTVd infection, and to clarify their role in symptom development. During the study, a systematic exploration of gene expression and endogenous phytohormones along the progression of disease will be conducted to better understand the physiological meaning of changes in the status of phytohormones associated to viroid infection. To assess the contribution of jasmonic acid (JA) and salicylic acid (SA) in response to PSTVd infection, JA- and SA-deficient transgenic potato lines will be used in order to determine whether the lack of phytohormones could be implicated in the systemic response and symptom characteristics.  Transcriptome analysis in leaves of systemically infected non-transgenic and transgenic potato lines will be employed to achieve higher resolution of differentially expressed genes (DEGs) involved in phytohormone signaling pathways and their crosstalk. In addition, the profiles of DEGs will be compared with profiles of some conserved miRNAs to identify viroid-responsive miRNAs implicated in the modulation of phytohormone signaling in potato during PSTVd infection. New findings can contribute to better understanding of the complexity of plant-viroid interactions and to support the development of new strategies for plant protection against viroids.