Expression of miRNAs and their targets in apple stem as determined by stem-loop RT-PCR and standard RT-PCR. A, Example of miRNAs and their targets that accumulate differentially between stem tissues, with dramatic difference in accumulation levels between tissues, indicative of target exclusion by miRNA action. Predicted miR164 target MdNAC1 was not detected in stem tissues. B, Differential expression of miRNAs and minor difference in target accumulation suggest general moderate target reduction. C, No obvious correlation between expression of the miRNA and some of the predicted targets. Real-time PCR reactions were performed in triplicate and the expression was normalised to apple ACTIN, with one of the periderm sample replicates acting as calibrator with a nominal value of 1. Error bars represent the means ± SE of three replicate PCRs. The Y axis represents relative expression of individual miRNA or mRNA. P, periderm; Ph, phloem; X, xylem.