The complete nucleotide sequence of the tobacco chloroplast genome: its gene organization and expression.

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.

New metabolites of Fusarium martii related to dihydrofusarubin.

Six strains of Fusarium martii produced fusarubin and dihydrofusarubins A and B. Further examination of strains, T-77 and T-127, showed that four additional metabolites were produced. By 1H and 13C NMR spectral analyses, these additional metabolites have been identified as 3-O-methyl and 3-O-ethyl ethers of fusarubin and dihydrofusarubin A. The methyl ethers are new compounds and showed moderate cytostatic activity against mouse leukemia L1210 culture cells as well as moderate antibiotic activity against leukemia L1210 culture cells as well as moderate antibiotic activity against Gram-positive bacteria and fungi. 3-O-Methyl and 3-O-ethyl ethers of dihydrofusarubin A were converted non-enzymically to the respective ethers of fusarubin under alkaline conditions. Since in addition, only dihydrofusarubin derivatives were formed when an acidic pH was maintained in the culture, it can be concluded that only these are true metabolites of Fusarium martii.

Six chloroplast genes (ndhA-F) homologous to human mitochondrial genes encoding components of the respiratory chain NADH dehydrogenase are actively expressed: determination of the splice sites in ndhA and ndhB pre-mRNAs.

Sequences (ndhA-F) homologous to human mitochondrial genes for components of the respiratory chain NADH dehydrogenase have been found in the chloroplast DNA of tobacco. The ndhA, D, E and F sequences corresponding to the mitochondrial URF1, 4, 4L and 5 are located in the small single copy region, the ndhB sequence corresponding to URF2 in the inverted repeat and the ndhC sequence corresponding to URF3 in the large single copy region of the chloroplast DNA. Northern blot hybridization revealed that all six ndh sequences are actively expressed in the chloroplasts. The ndhA and ndhB sequences contain single introns and the splice sites of their pre-mRNAs were determined by reverse transcription analysis. These findings suggest that potential components of an NADH dehydrogenase are synthesized in the chloroplasts.