A virus-based miRNA suppression (VbMS) system for miRNA loss-of-function analysis in plants

MicroRNAs (miRNAs) play key roles in plant development and defense against pathogens. To establish the function of individual miRNAs, gain‐of‐function analysis is usually done by overexpressing a specific miRNA in transgenic plants and has proved very effective. Loss‐of‐function analysis by the target mimic method is now also increasingly being used. The mimics expressed in the transgenic plants sequester a specific miRNA and lead to changed phenotypes that elucidate miRNA function. However, it takes time to obtain the transgenic plants. To avoid using transgenic plants, we have developed a virus‐based miRNA suppression system (VbMS) based on a Tobacco rattle virus vector. The target mimic sequences of miR156, miR319, or miR164 were introduced into the viral genomic RNA, which was then inoculated to Arabidopsis thaliana plants. The resulting phenotypes were consistent with previous reports from transgenic plants, and the expression of targets of the miRNAs was also increased showing that the activity of the miRNAs had been inhibited. VbMS developed here is validated for loss‐of‐function analysis of miRNA in plants. Moreover, since only simple agroinfiltration rather than transformation is needed, VbMS is suitable for large‐scale approaches to miRNA function analysis in plants. miRNAs play important roles in plant development and defense. In this manuscript, the authors describe a virus‐based miRNA suppression system in which the target mimic sequence is introduced into viral genomic RNA, creating a modified virus that can result in a loss‐of‐function phenotype in an infected plant. This simple process may be suitable for large‐scale approaches to miRNA function analysis in plants.