Observing the movement of specific molecules inside living cells can help us to explore how cells work and control various biological processes. Among biomolecules, RNAs are challenging to see owing to their low abundance, shorter lifespan and dynamic movement within the cell. Visualizing the dynamics of mRNA dynamics in live cells can help us understand their molecular and biochemical regulatory mechanisms. Despite this, existing non-invasive methods to tag and visualize RNAs are unable to achieve live imaging with super-resolution. Fluorescent RNAs (FRs) are biomolecular tags comprising single-stranded RNAs, also known as aptamers, that bind to ligands and fluoresce. These dyes are generally inert and don’t disrupt any cell function until they find their target; they only fluoresce once they have bound to their specific RNA target. While promising, existing green FRs, grapple with issues like photobleaching (irreversible loss of fluorescence from prolonged light exposure), insufficient brightness, and cellular ion or pH dependency.

Recently, Zuo et al. developed Okra505, a novel green FR for imaging mRNA dynamics in live cells. This bright, photostable green FR provides a clear visualization of mRNA in a range of cells and conditions and in diverse cellular and biochemical contexts, like formation of stress granules or localized mRNA accumulation. This new tool also minimizes any disruptions to the cell’s normal functions.