Small RNA Functions in Plant Embryos

Despite its fundamental importance, the molecular mechanisms that regulate plant embryogenesis remain largely uncharacterized. Studying the embryonic functions of microRNAs (miRNAs) will not only yield significant insights into the mechanistic basis of plant embryo development but will also contribute to our general understanding of how small regulatory RNAs influence cellular differentiation. More specifically, miRNAs are a class of ~21 nucleotide regulatory RNAs that are essential for both embryonic pattern formation and developmental timing in Arabidopsis thaliana. Because many plant miRNAs specifically repress transcripts encoding transcription factors, miRNAs likely have a large influence on the gene regulatory networks that control plant embryogenesis. We are investigating the functions of embryonic miRNAs with a combination of classic and modern molecular embryology techniques.

Fig. 1: MicroRNAs prevent precocious gene expression and enable pattern formation during plant embryogenesis. Shown here are confocal images of wild-type (left) and dicer-like1 (dcl1) mutant embryos (right), which are unable to make miRNAs. Both embryos have a transgene encoding a nuclear-localized GFP (green) with a miR156 target site. This miR156 sensor transgene is repressed by miR156 in wild-type embryos but not in dcl1 embryos due to the loss of miR156 activity. The loss of miRNAs, including miR156, in dcl1 embryos causes both cellular differentiation and developmental timing defects. (For details, see Nodine and Bartel, Genes & Development, 2010)