FIONA on Caenorhabditis elegans.

Despite much work, subcellular neurons of Caenorhabditis elegans have not been studied at nanometer resolution with millisecond time resolution. Nor has there been an effective way to immobilize C. elegans. Here we show that, without using anesthetic or paralyzing agents, fluorescence imaging with one-nanometer accuracy (FIONA) can be successfully applied to fluorescently labeled molecules within C. elegans nerves. GFP- and DENDRA2-labeled ELKS punctae can be localized with sub-10 nm accuracy in approximately 5 ms. Our results show that the protein ELKS is occasionally transferred by microtubule-based motors. This is the first example of FIONA applied to a living organism.