Introduction of the plasmid pKM101-associated muc genes into Saccharomyces cerevisiae

Bacteria-yeast shuttle plasmids containing the pKM101-associated muc genes were constructed by cloning an ARS TRP fragment into the plasmid pGW270 in both possible orientations. The insertion of Saccharomyces cerevisiae DNA into pGW270 had no effect on the mutator and protective phenotypes associated with the plasmid in Escherichia coli. Two such recombinant plasmids, pAA90 and pAA91 , were capable of efficient transformation of S. cerevisiae and were stably maintained in this organism. Hybridization experiments suggest that muc-specific mRNA was present in transformed yeast cells and a small amount was polyadenylated. The RNAs were not of a discrete size, all being smaller than the muc genes. The presence of the plasmid pAA91 , and to a lesser extent, pAA90 , in yeast resulted in a detectable increase in the reversion frequencies of three markers and in ultraviolet protection. These results are discussed in terms of studying the relationship of error-prone repair in bacteria and yeast and of developing improved yeast tester strains.     

Inverted repeats in the DNA of plasmid pCU1

Renaturable regions in the DNA strands of the N group plasmid pCU1 have been visualized as stem-loop structures by electron microscopy. Four such distinct structures are described, the smallest of which is within the loop of a larger one. The region of pCU1 in which these structures occur has several restriction sites. This and the availability of plasmid deletions and recombinants has permitted the mapping of these structures relative to one another and to the restriction and functional map of the plasmid. The replication and maintenance region of the plasmid is located within one of these stem-loop structures.     

Relationship between foliar composition of red-pine and jack-pine seedlings and vulnerability to Lophodermium needle-cast disease

Summary The Mn and Al content of needles from two-year-old jack pine (Pinus banksiana) seedlings was found to be more than twice that of red pine (Pinus resinosa). It is speculated that the high Mn and Al content of jack pine seedlings may impart some degree of resistance to needle cast disease caused byLophodermium pinastri. Contribution from the Soils Dept., Univ. of Wis., Madison, in cooperation with and supported in part by the Wisconsin Dept. of Natural Resources. Publication approved by the Director of the Wisconsin Agricultural Experiment Station.     

Genetic and Molecular Properties of an Infectious Antibiotic Resistance (R) Factor Isolated from Klebsiella

A Klebsiella strain of human origin that was resistant to ampicillin, chloramphenicol, kanamycin, neomycin, streptomycin, and tetracycline was found to have all of these resistances associated with a R factor and a satellite molecular species of deoxyribonucleic acid (DNA) with an average buoyant density of 1.710 in cesium chloride gradients. There was no evidence of the existence of DNA with other buoyant densities. The strain bears two separable mutations for chloramphenicol resistance, both of which are associated with the R factor (KR9). Exposure of the Klebsiella strain to acridine derivatives or to ethidium bromide (which was more efficient) resulted in partial losses of resistance accompanied by the disappearance of the satellite DNA peak or shifts in its density. The R factor and its component genes were conjugally transmitted across generic boundaries and maintained in new hosts with different efficiencies. The basis of this difference lies not only in the efficiency of conjugal transfer but also in the stability of the components after transfer. All of the resistance genes and the resistance transfer factor were cotransducible by phage Plkc from Escherichia coli. Partially resistant strains could be reconstituted to full resistance or to a recombined pattern of partial resistance by conjugation with donors having complementary resistance patterns. This recombination serves as an efficient mechanism for rescuing superinfecting genes that are otherwise intracellularly excluded. KR9 is an fi⁺ type of R factor which in the natural state does not appear to be as repressed in conjugal transfer as other R factors.     

Factors affecting the use of chloramphenicol acetyltransferase as a marker for Brassica genetic transformation

The CAT gene which codes for the enzyme chloramphenicol acetyltransferase was found to be ineffective as a reporter gene in cells and tissues of Brassica species. High levels of endogenous CAT activity were found to be widespread among this genus and did not appear to be distributed in a tissue- or cell-specific manner. Moreover, the presence of an inhibitor of CAT activity was discovered in Brassica napus and Brassica juncea. This inhibitor appeared to act selectively on bacterial CAT in transgenic plants. These findings provided an explanation for difficulties experienced in the detection of transgenic CAT activity in B. napus.     

Virulence of Agrobacterium tumefaciens strains with Brassica napus and Brassica juncea

Summary Brassica napus and Brassica juncea were infected with a number of Agrobacterium tumefaciens strains. Tumourigenesis was very rapid and extremely efficient on B. juncea with all but one of the strains. Tumourigenesis on B. napus varied widely. It was very efficient with the nopaline strains, was reduced with the succinamopine strain A281 and was very weak with the octopine strains. The latter observation was confirmed with six different B. napus rapeseed cultivars. The selectivity was due to differences in the virulence of Ti plasmids with B. napus, rather than the tumourigenicity of the T-DNA or virulence of the chromosomal genes associated with the strains. An exception was strain LBA4404. The virulence of the octopine strains was increased by coinfection with more virulent disarmed strains and by induction with acetosyringone.