Since the discovery of small RNAs and RNA silencing, RNA biology has taken a centre stage in cell and developmental biology. Small RNAs, but also mRNAs and other types of cellular and viral RNAs are processed at specific subcellular localizations. To fully understand cellular RNA metabolism and the various processes influenced by it, techniques are required that permit the sequence-specific tracking of RNAs in living cells. A variety of methods for RNA visualization have been developed since the 1990s, but plant cells pose particular challenges and not all approaches are applicable to them. On the other hand, plant RNA metabolism is particularly diverse and RNAs are even transported between cells, so RNA imaging can potentially provide many valuable insights into plant function at the cellular and tissue level. This Short Review briefly introduces the currently available techniques for plant RNA in vivo imaging and discusses their suitability for different biological questions.Lay Description
Proteins fulfil many important roles in cells and it has long been appreciated by cell biologists that their location within the cell is intricately linked to their function. The discovery of the green fluorescent protein has enabled tracking of specific proteins within cells by high-resolution fluorescence microscopy and thus enabled many breakthrough discoveries. In the last two decades multiple regulatory roles beyond the transfer of information from genes to the protein synthesis machinery have been discovered for ribonucleic acid (RNA). It is becoming clearer that the locations of RNAs in cells are also important for their function, but since there are no intrinsically fluorescent RNAs known, fluorescence imaging of RNA in cells is less straightforward than for proteins. Nevertheless a number of approaches have been developed that enable RNA imaging. In plants, the impermeant cell wall and numerous sources of intrinsic fluorescence limit the applicability of such methods and the number of studies using RNA imaging is still very small. This review compares RNA imaging techniques currently available for plant cells and highlights the novel insights they have already facilitated.