Abstract
Plant and animal microRNA (miRNA) pathways share many analogous components, the ARGONAUTE (AGO) proteins being foremost among them. We sought to ascertain the degree of functional conservation shared by Homo sapiens ARGONAUTE 2 (HsAGO2) and Arabidopsis thaliana ARGONAUTE 1 (AtAGO1), which are the predominant AGO family members involved with miRNA activity in their respective species. Transgenic Arabidopsis plants expressing HsAGO2 were indistinguishable from counterparts over-expressing AtAGO1, each group exhibiting the morphological and molecular hallmarks of miRNA-pathway loss-of-function alleles. However, unlike AtAGO1, HsAGO2 was unable to rescue the ago1–27 allele. We conclude that, despite the evolutionary gulf between them, HsAGO2 is likely capable of interacting with some component/s of the Arabidopsis miRNA pathway, thereby perturbing its operation, although differences have arisen such that HsAGO2 alone is insufficient to confer efficient silencing of miRNA targets in planta.
Highlights
MicroRNAs are endogenous small RNAs that direct the sequence-specific silencing of mRNA transcripts, providing a critical layer of gene regulation in both plants and animals (Pasquinelli, 2012)
EXPRESSION OF Homo sapiens ARGONAUTE 2 (HsAGO2) IN Arabidopsis RESULTS IN PLEIOTROPIC DEVELOPMENTAL DEFECTS A cDNA for HsAGO2 was placed under the control of a double 35S promoter and the resulting binary vector (35S:HsAGO2) was Frontiers in Plant Science | Plant Genetics and Genomics transformed into wild type Arabidopsis
The best-studied AGO proteins of each kingdom, Arabidopsis thaliana ARGONAUTE 1 (AtAGO1) and HsAGO2 are believed to share a high degree of functional conservation
Summary
MicroRNAs (miRNAs) are endogenous small RNAs (sRNAs) that direct the sequence-specific silencing of mRNA transcripts, providing a critical layer of gene regulation in both plants and animals (Pasquinelli, 2012). Much of the molecular machinery that oversees miRNA biogenesis and activity is shared between these kingdoms and, must have arisen prior to their divergence, though it is unclear whether a basal miRNA pathway was already in operation at this time (Axtell et al, 2011). From this shared origin, the plant and animal miRNA pathways have followed divergent evolutionary courses and there exists characteristic distinctions in the manner of their operation. The question of how the apparently similar set of components in the miRNA pathways of plants and animals has been modified so as to generate these functional differences is keenly relevant to our understanding of eukaryotic gene regulation
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