Expression profiling across wild and cultivated tomatoes supports the relevance of early miR482/2118 suppression for Phytophthora resistance

Plants possess a battery of specific pathogen resistance ( R- )genes. Precise R- gene regulation is important in the presence and absence of a pathogen. Recently, a microRNA family, miR482/2118, was shown to regulate the expression of a major class of R- genes , nucleotide-binding site leucine-rich repeats ( NBS-LRRs ). Furthermore, RNA silencing suppressor proteins, secreted by pathogens, prevent the accumulation of miR482/2118, leading to an upregulation of R- genes. Despite this transcriptional release of R -genes, RNA silencing suppressors positively contribute to the virulence of some pathogens . To investigate this paradox, we analysed how the regulation of NBS-LRRs by miR482/2118 has been shaped by the coevolution between Phytophthora infestans and cultivated and wild tomatoes. We used degradome analyses and qRT-PCR to evaluate and quantify the co-expression of miR482/2118 and their NBS-LRR targets. Our data show that miR482/2118-mediated targeting contributes to the regulation of NBS-LRRs in Solanum lycopersicum. Based on miR482/2118 expression profiling in two additional tomato species-with different coevolutionary histories with P. infestans -we hypothesize that pathogen-mediated RNA silencing suppression is most effective in the interaction between S. lycopersicum and P. infestans Furthermore, an upregulation of miR482/2118 early in the infection may increase susceptibility to P. infestans .