Lincomycin Treatment: A Simple Method to Differentiate Primary and Processed Transcripts in Rice (Oryza sativa L.) Chloroplasts

Visualizing full-length primary transcripts is helpful in identifying transcription initiation sites and mapping promoter regions of plastid genes and operons. Detection of primary unprocessed transcripts from certain regions of the plastid genome is difficult, and sometimes impossible, because of their rapid and extensive processing. We tested the effect of lincomycin, a prokaryotic protein synthesis inhibiter, on in vivo RNA processing activities in different types of rice plastid. Steady-state levels of RNA produced from the region of the rice plastid genome that includes thetrnV and 16s rRNA genes were analysed by using an RNase protection assay. Results show that sublethal lincomycin levels inhibit RNA processing in leaf chloroplasts and allow the accumulation of primary transcripts, easily distinguishable from processed and processing intermediates. These features were used to identify regions of the 16r andtrnV transcription start sites. This is the first report of the use of lincomycin for mapping plastidic transcripts.