The movement of coiled bodies visualized in living plant cells by the green fluorescent protein

Coiled bodies are nuclear organelles that contain components of at least th ree RNA-processing pathways: pre-mRNA splicing, histone mRNA 3'-maturation, and pre-rRNA processing. Their function remains unknown. However, it has b een speculated that coiled bodies may be sites of splicing factor assembly and/or recycling, play a role in histone mRNA S'-processing, or act as nucl ear transport or sorting structures. To study the dynamics of coiled bodies in living cells, we have stably expressed a U2B "-green fluorescent protei n fusion in tobacco BY-2 cells and in Arabidopsis plants. Time-lapse confoc al microscopy has shown that coiled bodies are mobile organelles in plant c ells. We have observed movements of coiled bodies in the nucleolus, in the nucleoplasm, and from the periphery of the nucleus into the nucleolus, whic h suggests a transport function for coiled bodies. Furthermore, we have obs erved coalescence of coiled bodies, which suggests a mechanism for the decr ease in coiled body number during the cell cycle. Deletion analysis of the U2B " gene construct has shown that the first RNP-80 motif is sufficient fo r localization to the coiled body.