Quantitative Fluorescence In Situ Hybridization Detection of Plant mRNAs with Single-Molecule Resolution.

Single-molecule FISH (smFISH) has been widely used in animal tissue to localize and quantify RNAs with high specificity. This protocol describes an smFISH method optimized for highly autofluorescent plant tissue. It provides details on fixation buffers and protocols to protect the integrity of plant samples. We also provide smFISH hybridization conditions to detect plant RNA with ~50 fluorescently labeled DNA oligonucleotides. In addition, this protocol provides instructions on linear spectral unmixing of smFISH signal from background autofluorescence by confocal microscopy and a method to quantify the smFISH spots that reflect the copy number of target RNA.