Biological and Molecular Evidence for the Transgenosis of Genes from Bacteria to Plant Cells

Abstract

Specialized transducing phages (X and 480) have been used as vectors in the transfer of genes We have tested for the possibility that bacterial genes can be transferred to, and then expressed within, plant cells. The experiments make use of the ability of specialized transducing phage (X, 480) to incorporate selected bacterial genes into their genome. These vector phage are simply added to plant cells in culture on fully defined media.For phenotypic expression, a sequence of gene transfer, maintenance, transcription, translation, and metabolic function must occur, except when the product of gene expression can function without translation (for example, a species of transfer RNA). After the initial transfer, the enzymic and structural elements for gene expression must be supplied by the plant cells. The overall phenomenon of transfer and subsequent expression has been termed transgenosis (1) to avoid a premature assumption of mechanisms inherent in the use of established terms, such as transduction, taken from bacterial genetics. Transgenosis is regarded as a particularly appropriate term when donor and recipient cells are separated widely by evolution and the mechanisms of gene transfer and maintenance (inheritance?) are obscure.The recipient cells for transgenosis were mostly haploid cell lines of Lycopersicon esculentum and Arabidopsis thaliana recently developed in this laboratory (2, 3). Haploidy is not essential for the present experiments, but has important implications for the future development of transgenosis (1).The biological detection of an advantageous transgenosis depended on survival and growth of plant cells on medium containing galactose and lactose as carbon sources. These environments are normally lethal (1, 4). Information for the metabolism of the sugars to usable sources of carbon was provided by the genes of the Escherichia coli galactose (gal) and lactose (lac) operons.A system where transgenosis might be a disadvantage was provided by "infection" with the E. coli mutant supF+ gene (also known as SulII +), which codes for a transfer RNA able to correct a nonsense mutation carried as a nonsense (amber) triplet in messenger RNA. Suppressor mutations lead to more mistakes in reading the genetic code and can be considered as unlikely to accumulate in higher organisms [see Watson (5) ]. If nonsense codons are vital to the life of plant cells, efficient suppression resulting from transgenosis of supF+ could be predicted to result in severe inhibition or death on normally optimal growth medium.Preliminary reports (3, 6) and a more detailed account of evidence and a discussion of background and results (1) have been presented. MATERIALS AND METHODSThe derivation and culture of haploid cell lines of Lycopersicon esculentum (tomato) ANU-H27-1 and Arabidopsis thaliana ANU-H872-1 have been described (2, 3). L. esculentum ANU-H27-1 was maintained on DBM3 medium (2)

Application of Tissue Culture for Plant Improvement

“…Similar approaches have been made with plants (4,22,29), including DNA-mediated transformation (28). Of particular interest are experiments in which free living ni-trogen fixing bacteria are to be associated with easily cultured, nonleguminous species.…”

Tissue Culture in the Production of Novel Disease‐resistant Crop Plants

“…Most of these experiments, however, did not take account of the alterations in gene expression which may occur in plant cells when the culture environment is changed. In the experiments described by Doy et al (1973a), for example, the increased growth of cells treated with hp gal+ phage on medium containing galactose could have been due to epigenetic ' physiological' adaptation by the plant cells to the different carbon source, especially since similar changes were observed in the uninoculated control calluses. On balance, it appears that bacterial genes transferred by transducing phage may be briefly expressed in plant cells (Kleinhofs & Behki, 1977), although there is no evidence that bacterial genes can be directly incorporated into the recipient plant genome, such that a heritable change in plant phenotype would result.…”

Bacteriophage T3 and bacteriophage T7 virus-host cell interactions.

“…Interactions with Eucaryotic Systems Prompted by the spectacular finding of Merril and co-workers (134, 311) that Xpgal induces galactose-1-phosphate uridylyltransferase in galactosemic human cells and by successful phage transduction of E. coli genes into plant cells (101), the interactions between phage and eucaryotic systems attracted the interest of molecular biologists (cp. 309,310).…”