RESUMO
We have applied the arbitrarily primed polymerase chain reaction (AP-PCR) technique to the analysis of the relationships among six japonica and indica cultivars, and four wild species of rice. Chosen were four primers of arbitrary sequence that gave multiple amplification products when rice DNA was used as template. Among a total of 50 bands scored, 44 were polymorphic, which was sufficient to distinguish the species used in this study. It is apparent from the comparisons of genetic distances that cultivated rice (Oryza sativa) exhibits closest molecular affinity to wild O. rufipogon, suggesting that the origin of cultivated rice is from O. rufipogon. In a dendrogram of cultivated rice and O. rufipogon from different regions, japonica and indica rice were most closely clustered with O. rufipogon from China and India, respectively. Japonica and indica subspecies showed closer affinity with O. rufipogon from different origins than with each other, supporting a hypothesis of multi-centers of the origin of rice cultivation.
Assuntos
Oryza/genética , Polimorfismo Genético , Agricultura , Sequência de Bases , Primers do DNA/genética , DNA de Plantas/genética , Amplificação de Genes , Dados de Sequência Molecular , Oryza/classificação , Reação em Cadeia da Polimerase , Especificidade da EspécieRESUMO
The essential cell division genes ftsQ, ftsA and ftsZ map in a cluster of cell envelope genes located at two minutes on the Escherichia coli genetic map and appear to constitute an atypical operon. These closely clustered genes are all transcribed in the same direction and yet each of these genes was independently cloned on a multicopy plasmid and found to be expressed. Tn5 insertion mutagenesis of this region confirmed that these genes were independently expressed, indicating that each of these genes has its own promoter. However, maximum expression of the distal ftsZ gene required the promoter for the proximal ftsQ gene. The proximal ftsZ promoter was located within the ftsA structural gene and the proximal ftsA promoter was located within the ftsQ structural gene. No transcription terminators were evident from the DNA sequence analysis of this region. The sequence analysis also revealed that the termination codon for ftsQ overlapped the initiation codon of the ftsA gene and that the ftsA and ftsZ genes were separated by 60 base-pairs. The ftsQ gene product has a calculated Mr of 31,432 and the ftsA gene product has a calculated Mr of 45,327. The structure and expression of these genes are discussed.
Assuntos
Escherichia coli/genética , Genes Bacterianos , Autorradiografia , Sequência de Bases , Divisão Celular , Clonagem Molecular , Códon , Elementos de DNA Transponíveis , DNA Bacteriano , Eletroforese em Gel de Poliacrilamida , Escherichia coli/citologia , Óperon , PlasmídeosRESUMO
The nucleotide sequence of a 1.8-kb fragment of Escherichia coli DNA containing the essential cell division gene ftsZ is reported. The FtsZ protein has an Mr of 40294 and has 23% charged residues with a calculated isoelectric point of 4.9. The codon usage of the ftsZ gene reflects that of a highly expressed gene. Also located on this DNA fragment is the 3' end of the ftsA gene and the 5' end of the envA gene. These designations were confirmed by locating Tn5 insertions within the ends of these genes that inactivate each of these genes. A potential promoter for ftsZ overlapped the 3' end of the ftsA gene. A Tn5 insertion was located within the 3' end of the ftsA and within this potential promoter. No transcription terminators were evident between ftsA and ftsZ or between ftsZ and envA.
