The sym plasmid pRP2JI and at least two other loci of Rhizobium leguminosarum biovar phaseoli can confer resistance to infection by the virulent bacteriophage RL38

Abstract The virulent Rhizobium bacteriophage RL38 did not form plaques on R.leguminosarum by phaseoli but did so at high efficiency on a derivative of that strain lacking its symbiotic plasmid pRP2JI. Other strains with large deletions in pRP2JI which removed many nod and nif genes retained resistance to RL38, showing that the gene which confers phage resistance lies elsewhere on the plasmid. Although the wild-type strain of R. leguminosarum bv. phaseoli failed to plate RL38, it was possible to transduce chromosomal markers into this strain, indicating that the 'block' was not at an early stage in the infection process. Two different recombinant plasmids obtained from a clone bank of genomic DNA of R. leguminosarum bv. phaseoli , which appeared to have no DNA in common, both conferred resistance to RL38. Surprisingly, the DNA cloned in each of these plasmids did not originate from pRP2JI. Therefore, several different loci both on the Sym plasmid and elsewhere on the bacterial genome can be involved in conferring resistance to this bacteriophage.     

Comparison of the phospholipid requirements and molecular form of CTP : phosphocholine cytidylyltransferase from rat lung, kidney, brain and liver

The cytidylyltransferase activity in fresh cytosol from different tissues of the rat was measured in the absence and presence of phosphatidylglycerol. In all cases addition of this lipid produced large increases in enzyme activity. Agarose gel (A-5.0) filtration profiles of the enzyme activities indicated that the L-form of the enzyme (190 000 molecular weight) predominated in liver, brain, kidney, and fetal lung. However, adult lung cytosol contained 70--80% of the activity in the H-form (molecular weight greater than or equal to 5 x 10(6)). Removal of phospholipid material from the alveolar spaces by lavage produced a significant reduction of the H-form of the enzyme in the cytosol fraction. The L-form of the cytidylyltransferases from fetal lung and adult liver, kidney, and brain all possess the same specificities for activation by phospholipids in vitro. In all cases, phosphatidylglycerol was the most potent activator at 0.2 mM. Lysophosphatidylethanolamine stimulated enzyme activity, whereas lysophosphatidylglycerol was a potent inhibitor. These studies implicate the role of acidic phospholipids in the regulation of cytidylyltransferase activity in vivo and the existence of a common L-form of the enzyme in serveral tissues of the rat.     

The immunoassay of gibberellins

The development of sensitive and specific solid-phase enzyme immunoassays for gibberellic acid and gibberellins A₄ and A₇ is reported. The use of antisera of high apparent affinity (K_a over 10¹⁰ l mol^-1) in conjunction with alkaline phosphatase-labeled gibberellins allows, with minimum procedural effort, the quantitative determination of sub-picogram amounts of these gibberellins. The assays reported here are applicable to most gibberellins and can be set up with 1–1.5 mg of starting material. They represent the most sensitive methods for gibberellin determination known.Abbreviations GA gibberellin - GA₃ gibberellic acid - TLC thin-layer-chromatography     

Generic distribution patterns in subsaharan African Rubiaceae (Angiospermae)

A survey of the distribution of the Rubiaceae from subsaharan African (continental part: 1,900 species in 164 genera; Madagascar: 675 species in 83 genera) is given. Genera are classified in nine major distribution patterns, most of which are further subdivided. General statistics of the data are given, and the patterns are discussed in the light of (i) the phytogeographical literature relating to tropical Africa and (ii) existing evolutionary hypotheses on the Rubiaceae.