this work represents the initial step in uncovering a new layer of regulation mediated by endogenous sRNAs that may contribute in the massive alteration of the transcriptome associated to plant-virus interactions and viral symptoms. We consider that both host-derived sRNAs and vsRNAs have a crucial

Small RNAs (sRNAs) play important roles in plant development and host-pathogen interactions. Several studies have highlighted the relationship between viral infections, endogenous sRNA accumulation and transcriptional changes associated with symptoms. However, few studies have described a global analysis of sRNAs (endogenous and viral) by comparing related viruses that produce differential symptomatology at early stages of infection, especially before viral accumulation reaches systemic tissues. An sRNA deep-sequencing of Arabidopsis thaliana leaf samples infected either with Oilseed rape mosaic virus (ORMV) or crucifer-infecting Tobacco mosaic virus (TMV-Cg) with contrasting symptomatology at two early stages of infection (2 and 4dpi) was performed. At early stages, both viral infections strongly alter the patterns of several types of sRNA species in distal tissues with no virus suggesting a systemic signaling process foregoing virus accumulation. We also provided an vsRNA profile report for both viruses along with a set of potential targets of ORMV- and TMV-Cg-derived vsRNAs..We found a distinctive temporal biphasic microRNA accumulation process in infected plants in contrast to mock-inoculated plants. We then focused on differential levels of endogenous sRNAs derived from protein coding genes and explored their potential role in expression control. A correlation between many of these sRNAs and the associated mRNA transcripts was detected, suggesting that an unknown recursive mechanism might be involved in a regulatory circuit encompassing this sRNA/mRNA equilibrium. This work represents the initial step in uncovering another layer of regulation mediated by endogenous sRNAs that may contribute to the massive alteration of the transcriptome associated to plant-virus interactions.