A Visual Reporter System for Analyzing Small RNA-Triggered Local and Systemic Silencing of an Endogenous Plant Gene

Plant small RNAs (sRNAs) silence highly sequence complementary target mRNAs locally in a cell-autonomous manner but can also move long distances to induce systemic gene silencing in distal tissues. Unfortunately, the lack of appropriate experimental systems has hampered the identification of the factors determining the induction and spread of local and systemic gene silencing triggered by plant sRNAs. Here we describe a visual reporter system in which both local and systemic silencing of Nicotiana benthamiana SULFUR (NbSu) gene is triggered by the agroinfiltration of an artificial sRNA construct. Agroinfiltrated areas show strong and uniform bleaching while apical non-agroinfiltrated leaves display a characteristic near-vein chlorosis. This visual reporter system should facilitate the identification of the genetic, molecular, and/or environmental factors regulating both local and systemic silencing activities of plant sRNAs.