In silico prediction of miRNAs targeting ToLCVand their regulation in susceptible and resistant tomato plants

Tomato leaf curl disease is one of the main constraints in tomato production worldwide. It is induced by viruses including Tomato leaf curl virus (ToLCV). Plant viruses can both induce and be themselves targeted by gene silencing machinery. Certain animal viruses were found to be targeted by host miRNAs but, there is no similar experimental report for plant viruses. In this study, we investigated if tomatoencoded miRNAs target ToLCV using an in silico analysis. Results showed that ToLCV can be targeted by three tomato miRNAs, named miR156, miR159, and miR403. Following virus infection of susceptible tomato plants cv Moneymaker, miR159 and miR403 were upregulated, while miR156 was unchanged. In the plants of the resistant tomato variety PS550, that accumulated 50-fold less viral DNA and did not show disease symptoms, miR156 was upregulated, while the two others remained unchanged. In addition, the expression level of three genes known as targets of these miRNAs, i.e. SPL6b, MYB33 and AGO2a, was measured in both susceptible and resistant tomato varieties by qRT-PCR. The possible role of the predicted miRNAs and regulation of their target genes in symptom development by ToLCV is discussed.