Molecular Manipulation of the MiR160/ Expression Module Impacts Root Development in

In (), microRNA160 (miR160) regulates the expression of (), and throughout development, including the development of the root system. We have previously shown that in addition to DOUBLE-STRANDED RNA BINDING1 (DRB1), DRB2 is also involved in controlling the rate of production of specific miRNA cohorts in the tissues where is expressed in wild-type plants. In this study, a miR160 overexpression transgene () and miR160-resistant transgene versions of and ( and ) were introduced into wild-type plants and the and single mutants to determine the degree of requirement of DRB2 to regulate the miR160 expression module as part of root development. Via this molecular modification approach, we show that in addition to DRB1, DRB2 is required to regulate the level of miR160 production from its precursor transcripts in roots. Furthermore, we go on to correlate the altered abundance of miR160 or its , and target genes in the generated series of transformant lines with the enhanced development of the root system displayed by these plant lines. More specifically, promotion of primary root elongation likely stemmed from enhancement of miR160-directed expression repression, while the promotion of lateral and adventitious root formation was the result of an elevated degree of miR160-directed regulation of expression, and to a lesser degree, and expression. Taken together, the results presented in this study identify the requirement of the functional interplay between DRB1 and DRB2 to tightly control the rate of miR160 production, to in turn ensure the appropriate degree of miR160-directed , and gene expression regulation as part of normal root system development in .