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Searching for the mechanism that mediates the mefenoxam-acquired resistance phenomenon in Phytophthora infestans and how it is regulated

Juliana Gonzalez Tobon: Universidad de los Andes

<div><em>Phytophthora infestans</em>, the causal agent of late blight disease of potatoes and tomatoes, is mainly controlled by the use of fungicides. Populations of <em>P. infestans </em>that are resistant to commonly used fungicides have already been reported. Aside from natural resistance, several studies have shown that isolates of <em>P. infestans </em>that are originally sensitive to the fungicide mefenoxam are able to acquire resistance to this fungicide when exposed to sub-lethal concentrations of it. This phenomenon termed ‘mefenoxam-acquired resistance’ has been observed in different species of the <em>Phytophthora </em>genus and seems to be unique to mefenoxam. The first objective of this study was to elucidate the molecular mechanism mediating this acquisition of resistance. Given that mefenoxam seems to interfere with the pathogen’s RNA polymerase I, both <em>in silico </em>and experimental analyses were carried out to evaluate if its activity might be affected by the phenomenon. Furthermore, genes that are differentially expressed between originally sensitive isolates and those same isolates after acquiring resistance were identified and further analyzed. The second objective was to investigate if there is a regulatory epigenetic process, such as small non-coding RNAs or chromatin remodeling, mediating this mechanism. This study will narrow-down all possible hypotheses and generate new questions that might contribute to the comprehension of epigenetic and molecular processes of this pathogen.</div>

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