PubMed · 368654
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J D Watson. 1979-03-08. Let us stop regulating DNA research.. https://doi.org/10.1038/278113a0
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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.
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Because it is now clear that archaebacteria may be as distinct from eubacteria as either group is from eukaryotic cells, and because a specifically archaebacterial ancestry has been proposed for the nuclear-cytoplasmic component of eukaryotic cells, we undertook to characterize, for the first time, the ribosomal RNA cistrons of an archaebacterium (Halobacterium halobium). We found these cistrons to be physically linked in the order 16S-23S-5S, and obtained evidence that they are also transcribed from a common promoter(s) in the order 5'-16S-23S-5S-3'. We showed that, although slightly larger immediate precursors of 16S and 23S are readily seen, no common precursor of both 16S and 23S can be easily detected in vivo. In all these respects the archaebacterium H. halobium is like a eubacterium and unlike the nuclear-cytoplasmic component of eukaryotic cells. We found, however, that it differs from eubacteria of comparable (large) genome size in having only one copy of the rRNA gene cluster per genome.