PubMed · 6340199
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G Kolata. 1983-04-15. Control element found within structural gene.. https://doi.org/10.1126/science.6340199
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Agrobacterium transfers DNA into plant cells, leading to tumors, hairy roots (HR), and natural genetically modified organisms (nGMOs). Transferred DNAs (T-DNAs) from agrobacteria and T-DNA-derived cellular T-DNAs (cT-DNAs) from nGMOs vary considerably and may carry up to 15 different genes. Among these, opine synthase (ops) genes encode the synthesis of opines used as nutrients by the agrobacteria. Earlier studies predicted large numbers of naturally transformed plant species, but only few have been identified and studied so far. We therefore developed a general method to detect cT-DNAs in all publicly available whole genome sequences (WGS) and Sequence Read Archive (SRA) data from land plants. To avoid false positives, we only retained DNA sequences coding for T-DNA proteins. A total of 2614 nGMO species were identified, most are eudicots. However, cT-DNAs were also found in 82 mosses and 75 ferns, showing that Agrobacterium can also generate natural transformants among the early land plants. Analysis of 149 cT-DNA maps revealed different types of T-DNAs. Most notably, these included small T-DNAs (mini T-DNAs) with a single opine synthase gene. Mini T-DNAs are not expected to induce tumors or HRs. The predominance of mini cT-DNAs in mosses and ferns, and the presence of more complex cT-DNAs in spermatophytes, indicate that mini T-DNAs represent the earliest types of T-DNA. Our study also detected unusual T-DNA integration patterns, with multiple copies spread out over several hundreds of kilobases.
TdcB activity expressed from the chromosomal gene and LacZ expression from single-copy tdc-lacZ transcriptional and translational fusions were measured in Escherichia coli strains harboring mutations in the genes encoding DNA gyrase, topoisomerase I and the HU protein. The pattern of tdc operon expression in these mutants suggests that relaxation of supercoiled DNA enhances tdc transcription in vivo.
The effects of mitomycin C on C1857-controlled recombinant gene expression have been explored in E. coli cultures when the drug was added simultaneously to the thermal induction. A significantly improved yield of homologous, heterologous and chimeric fusion proteins was observed in E. coli MC1061 and GE864 (a MC4100 derivative) thermoinduced cells. This feature was not detected in other E. coli strains and does not involve a gene dosage mechanism but a strain-dependent stimulation of gene expression unrelated to the RecA protease activity.