Trip to ER: MicroRNA-mediated translational repression in plants.

miRNAs elicit gene silencing at the post-transcriptional level by several modes of action: translational repression, mRNA decay, and mRNA cleavage. Studies in animals have suggested that translational repression occurs at early steps of translation initiation, which can be followed by deadenylation and mRNA decay. Plant miRNAs were originally thought to solely participate in mRNA cleavage, but increasing evidence has indicated that they are also commonly involved in translational inhibition. Here we discuss recent findings on miRNA-mediated translational repression in plants. The identification of AMP1 in Arabidopsis as a protein required for the translational repression but not the mRNA cleavage activity of miRNAs links miRNA-based translational repression to the endoplasmic reticulum (ER). Future work is required to further elucidate the miRNA machinery on the ER.