RESUMO
The complete nucleotide sequence (155 844 bp) of tobacco (Nicotiana tabacum var. Bright Yellow 4) chloroplast DNA has been determined. It contains two copies of an identical 25 339 bp inverted repeat, which are separated by a 86 684 bp and a 18 482 bp single-copy region. The genes for 4 different rRNAs, 30 different tRNAs, 39 different proteins and 11 other predicted protein coding genes have been located. Among them, 15 genes contain introns. Blot hybridization revealed that all rRNA and tRNA genes and 27 protein genes so far analysed are transcribed in the chloroplast and that primary transcripts of the split genes hitherto examined are spliced. Five sequences coding for proteins homologous to components of the respiratory-chain NADH dehydrogenase from human mitochondria have been found. The 30 tRNAs predicted from their genes are sufficient to read all codons if the ;two out of three' and ;U:N wobble' mechanisms operate in the chloroplast. Two sequences which autonomously replicate in yeast have also been mapped. The sequence and expression analyses indicate both prokaryotic and eukaryotic features of the chloroplast genes.
RESUMO
The 50 S subunit of chloroplast ribosomes was prepared from tobacco leaves. The proteins were fractionated and the N-terminal amino acid sequence of a 14 kDa protein was determined. This sequence matches the N-terminal sequence deduced from ORF55 located between ndhF and trnL on the small single-copy region of tobacco chloroplast DNA. The deduced protein shows homology to E. coli and B. stearothermophilus L32 proteins, and it has been named as CL32 and ORF55 as rpl32. The tobacco chloroplast genome therefore contains 21 different ribosomal protein genes.
Assuntos
Cloroplastos/metabolismo , Genes de Plantas , Nicotiana/genética , Plantas Tóxicas , Proteínas Ribossômicas/genética , Sequência de Aminoácidos , Escherichia coli/genética , Dados de Sequência Molecular , Plantas/genética , Conformação Proteica , Homologia de Sequência do Ácido NucleicoRESUMO
Transcription of rps2, rps4, rps7, rps11, rps14, rps15, rps18, rpl20, rpl33 and rpl36 from the tobacco chloroplast genome has been studied. Northern blot analysis has revealed that all these genes are transcribed in the chloroplast. Multiple transcripts were detected for all the genes and amounts of the transcripts were quite different among the ten genes. These ten ribosomal protein genes together with the ten other ribosomal protein genes published previously were complied and compared. Four out of the twenty genes contain introns, possible secondary structures of which are presented.