Assistant Professor Department of Plant Pathology and Crop Physiology at LSU Baton Rouge, Louisiana
Body of Abstract: RNA silencing is pivotal regulatory machinery to program gene expression in stress responses and many biological processes. The accumulations of Argonaute (AGO) proteins, the key component of RNA silencing are fine-turned by multiple layers of regulations. To identify new RNA silencing components associated with AGO2, the major Arabidopsis AGO that promotes plant antibacterial resistances, we found a clade of DDX3-like DEAD-box RNA helicases, RH11/RH37/RH52, are new interactors of AGO2 and AGO1. Upon the infection of the bacterial pathogen Pseudomonas syringae pv. Tomato, the expression of RH11/RH37/RH52 is decreased and promotes plant immunity via increasing the accumulation of AGO2 protein. Here we showed that excessive RH11 helicases unwinding double-stranded sRNAs into single-stranded sRNAs would attenuate the loading of small RNA duplexes into AGO proteins. As the AGO protein is more stable after incorporating sRNA, the overexpression of these helicases decreases the level of AGO-sRNA association. It leads to AGO proteins decreasing. We found that the helicase activity of RH11/RH37/RH52 indirectly modulates the homeostasis of AGO protein accumulation. Intriguingly, the efficiency of AGO2 gene silencing is facilitated by the RH11 direct association due to RH11 unwinding the cleavage product more sufficiently. Thus, we uncover the two roles of RH11 in gene silencing including enhancing AGO protein function on RNA cleavage by directly binding to AGO and indirectly modulating the homeostasis of AGO protein by unwinding duplex small RNAs.