Phylogenetic comparative analysis of RNA structure on Macintosh computers

A Macintosh Hypertalk program (Hypercard ‘stack’)for use in phylogenetic comparative analysis of RNA structureis described. The program identifies covariations and compensatorychanges in RNA sequence alignments, for use in the constructionof secondary structure models or the identification of tertiaryinteractions. The results of an analysis are presented eitheras a list of positions in the alignment which covary, or asa 2-dimensional matrix in which potential helices in the secondarystructure appear as diagonal patterns. Received on January 7, 1991; accepted on March 19, 1991     

Uptake,Transport and Storage of Cardenolides in Foxglove. Cardenolide Sinks and Occurrence of Cardenolides in the Sieve Tubes of Digitalis lanata1

Cardiac glycoside transport was investigated on the organ and whole plant level. Uptake experiments were carried out with shoot and root cultures of Digitalis lanata. In both systems primary cardenolides, i.e., those with a terminal glucose in their oligosaccharide side chain, were taken up against their concentration gradient, whereas the glucose-free secondary cardenolides were not. Active uptake of primary cardenolides was further evidenced by KCN inhibition of uptake. Using plantlets grown in vitro the long-distance transport of primary cardenolides from the leaves to the roots was demonstrated. Cardenolides were also detected in etiolated leaves, induced on plants with green leaves, which are supposed to be unable to synthezise cardenolides de novo, providing further evidence for long-distance transport. Several primary cardenolides were detected in the honeydew excreted by aphids fed on Digitalis lanata leaves, indicating that the phloem is a transporting tissue for cardenolides. On the other hand, the xylem sap obtained by applying the pressure-chamber technique was cardenolide-free. It was concluded that in Digitalis primary cardenolides serve as both the transport and the storage form of cardenolides. After their synthesis they are either stored in the vacuoles of the source tissue or loaded into the sieve tubes, from which they are unloaded at other sites where they are trapped in the vacuoles of the respective sink tissue.     

Mutational analysis of slyD, an Escherichia coli gene encoding a protein of the FKBP immunophilin family

slyD encodes a 196 amino acid polypeptide that is a member of the FKBP family of cis–trans peptidyl–prolyl isomerases (PPIases). slyD mutations affect plaque formation by the phage φX174 by blocking the action of the phage lysis protein E. Here we describe the selection of a set of spontaneous slyD mutations conferring resistance to the expression of gene E from a plasmid. These mutations occur disproportionately in residues of SlyD that, based on the structure of the prototype mammalian FKBP12, make ligand contacts with immunosuppressing drug molecules or are conserved in other FKBP proteins. A wide variation in the plating efficiency of φX174 on these E  ^R strains is observed, relative to the parental, indicating that these alleles differ widely in residual SlyD activity. Moreover, it is found that slyD mutations cause significant growth rate defects in Escherichia coli B and C backgrounds. Finally, overexpression of slyD causes filamentation of the host. Thus, among the FKBP genes found in organisms across the evolutionary spectrum, slyD is unique in having three distinct drug-independent phenotypes.     

Evaluation of the Mast ID and API 50CH systems for identification of Listeria spp

A multipoint inoculation technique (Mast ID) for the identification and species determination of Listeria monocytogenes (sensu strictu) and six other species of the genus Listeria was evaluated. This was compared with the commercially available API 50CH system. Both methods successfully identified all 123 strains tested. The Mast ID system is inexpensive and utilizing a multipoint inoculation technique permits the screening of up to 21 isolates per 9-cm petri dish. The API 50CH system was more expensive and time consuming and is therefore suitable only for the examination of smaller numbers of strains.