Evidence that XRN4, an Arabidopsis homolog of exoribonuclease XRN1, preferentially impacts transcripts with certain sequences or in particular functional categories.

One of the major players controlling RNA decay is the cytoplasmic 5'-to-3' exoribonuclease, which is conserved among eukaryotic organisms. In Arabidopsis, the 5'-to-3' exoribonuclease XRN4 is involved in disease resistance, the response to ethylene, RNAi, and miRNA-mediated RNA decay. Curiously, XRN4 appears to display selectivity among its substrates because certain 3' cleavage products formed by miRNA-mediated decay, such as from ARF10 mRNA, accumulate in the xrn4 mutant, whereas others, such as from AGO1, do not.

Arabidopsis thaliana XRN2 is required for primary cleavage in the pre-ribosomal RNA.

Three Rat1/Xrn2 homologues exist in Arabidopsis thaliana: nuclear AtXRN2 and AtXRN3, and cytoplasmic AtXRN4. The latter has a role in degrading 3' products of miRNA-mediated mRNA cleavage, whereas all three proteins act as endogenous post-transcriptional gene silencing suppressors. Here we show that, similar to yeast nuclear Rat1, AtXRN2 has a role in ribosomal RNA processing.

High-throughput approaches for miRNA expression analysis.

miRNAs have emerged as key regulators of gene expression in both plants and animals. These small (generally 21-22 nt) RNA molecules, originated from primary "hairpin" transcripts, can induce translational suppression or direct mRNA cleavage. Similar to regular mRNAs, the expression of miRNAs is highly regulated.

Direct detection of small RNAs using splinted ligation.

This protocol describes a method for direct labeling and detection of small RNAs present in total RNA by splinted ligation. The assay uses a small RNA-specific bridge oligonucleotide to form base pairs with the small RNA and a 5'-end-radiolabeled ligation oligonucleotide. The captured small RNA is directly labeled by ligation.