Widespread Translational Inhibition by Plant miRNAs and siRNAs

TLDR

Plant miRNAs typically silence targets by endonucleolytic cleavage, and the decapping factor VARICOSE is also required for translational repression, indicating conserved mechanisms with animals. Arabidopsis mutants show that miRNA‑ and siRNA‑mediated silencing includes a widespread translational inhibition component, genetically separable from cleavage and dependent on AGO1/AGO10 and the microtubule‑severing enzyme katanin.

Abstract

High complementarity between plant microRNAs (miRNAs) and their messenger RNA targets is thought to cause silencing, prevalently by endonucleolytic cleavage. We have isolated Arabidopsis mutants defective in miRNA action. Their analysis provides evidence that plant miRNA–guided silencing has a widespread translational inhibitory component that is genetically separable from endonucleolytic cleavage. We further show that the same is true of silencing mediated by small interfering RNA (siRNA) populations. Translational repression is effected in part by the ARGONAUTE proteins AGO1 and AGO10. It also requires the activity of the microtubule-severing enzyme katanin, implicating cytoskeleton dynamics in miRNA action, as recently suggested from animal studies. Also as in animals, the decapping component VARICOSE (VCS)/Ge-1 is required for translational repression by miRNAs, which suggests that the underlying mechanisms in the two kingdoms are related.