Transcriptional activities of the chloroplast-nuclei and proplastid-nuclei isolated from tobacco exhibit different sensitivities to tagetitoxin: implication of the presence of distinct RNA polymerases.
We examined the effects of tagetitoxin, a potent inhibitor of RNA polymerases from chloroplasts and Escherichia coli, on the transcriptional activities of chloroplast- and proplastid-nuclei (nucleoids) isolated from mature tobacco (Nicotiana tabacum L.) leaves and cultured tobacco cells (line BY-2), respectively. Transcription by the isolated chloroplast-nuclei was effectively inhibited by tagetitoxin (95-99% reduction at 10 microM tagetitoxin), but transcription by the isolated proplastid-nuclei was only partially inhibited (40-50% reduction) by this compound. Southern hybridization experiments revealed that the transcription of various plastid genes (psbA, atpA, rpoB, psaA/B, atpB, rbcL, petB, rpl16, and rrn23) was sensitive to tagetitoxin in the isolated chloroplast-nuclei, whereas the transcription of the same genes was relatively resistant to this compound in the isolated proplastid-nuclei. These results suggest that; (i) distinct RNA polymerase activities with different sensitivities to tagetitoxin are present in plastids, (ii) a tagetitoxin-sensitive RNA polymerase is the major RNA polymerase in chloroplasts whereas a tagetitoxin-insensitive enzyme is major in proplastids, and (iii) both RNA polymerases can transcribe various plastid genes.
Sakai
A
A
Department of Biological Sciences, Graduate School of Science, University of Tokyo, Japan. sakai@biol.s.u-tokyo.ac.jp
Saito
C
C
Inada
N
N
Kuroiwa
T
T
D001312:Aurintricarboxylic Acid / Q000378:metabolism; D001427:Bacterial Toxins / Q000494:pharmacology*; D002467:Cell Nucleus / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D003609:Dactinomycin / Q000494:pharmacology; D003998:Dicarboxylic Acids / Q000494:pharmacology*; D017343:Genes, Plant / Q000187:drug effects; D007527:Isoenzymes / Q000378:metabolism; D007700:Kinetics; D009943:Organophosphorus Compounds / Q000494:pharmacology*; D010947:Plants, Toxic; D018087:Plastids / Q000378:metabolism; D018749:RNA, Plant / Q000096:biosynthesis* / Q000235:genetics; D014026:Nicotiana / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects*; D014544:Uridine Triphosphate / Q000378:metabolism
D001427:Bacterial Toxins; D003998:Dicarboxylic Acids; D007527:Isoenzymes; D009943:Organophosphorus Compounds; D018749:RNA, Plant; D003609:Dactinomycin; D001312:Aurintricarboxylic Acid; C062221:tagetitoxin; D012321:DNA-Directed RNA Polymerases; D014544:Uridine Triphosphate