Biomedical subjects

P Forsman

Publications and source records attributed to P Forsman.

5 recordsLinked to original sources

PubMed2006

Independence of genetic geographical variation between photoperiodic diapause, circadian eclosion rhythm, and Thr-Gly repeat region of the period gene in Drosophila littoralis.

Drosophila littoralis is a latitudinally widespread European species of the Drosophila virilis group. The species has ample genetic variation in photoperiodism (adult diapause) and circadian rhythmicity (pupal eclosion rhythm), with adaptive latitudinal clines in both of them. The possible common genetic basis between the variability of photoperiodism and circadian rhythms was studied by a long-term crossing experiment. A northern strain (65 degrees N) having long critical day length (CDL = 19.9 h) for diapause, early phase of the entrained rhythm in LD 3:21 (psi(LD3:21) = 12.3 h), and short period (tau= 18.8 h) of the free-running rhythm for the eclosion rhythm was crossed with a southern strain (42 degrees N) having short CDL (12.4 h), late eclosion phase (psi(LD3:21) = 20.2 h), and long period (tau= 22.8 h). After 54 generations, including free recombination, artificial selection, and genetic drift, a novel strain resulted, having even more "southern" diapause and more "northern" eclosion rhythm characteristics than found in any of the geographical strains. The observed complete separation of eclosion rhythm characteristics from photoperiodism is a new finding in D. littoralis; in earlier studies followed for 16 generations, the changes had been mostly parallel. Evidently, the genes controlling the variability of the eclosion rhythm and photoperiodism in D. littoralis are different but closely linked. To test for the possible gene loci underlying the observed geographical variability, the period gene was studied in 10 strains covering all the known clock variability in D. littoralis. The authors sequenced the most suspected Thr-Gly region, which is known to take part in the adaptive clock variability in Drosophila melanogaster. No coding differences were found in the strains, showing that this region is not included in the adaptive clock variability in D. littoralis.

Amino Acid Sequence↗

PubMed1995

Genome homology and superinfection immunity between temperate and virulent Lactobacillus delbrueckii bacteriophages.

The presence of short homologous DNA segments along the genomes of the temperate phage mv4 and the virulent phages LL-H, LL-K and JCL1032 of Lactobacillus delbrueckii was demonstrated with Southern hybridizations. One of these segments, the 2,817 nt MIS element of phage mv4, was further characterized by nucleotide sequence analysis and by superinfection immunity studies.

Bacteriophages↗

PubMed1994

Repeated sequences and the sites of genome rearrangements in bacteriophages of Lactobacillus delbrueckii subsp. lactis.

We have sequenced the KIS-element, a 1.5 kb insertion segment present in the genome of Lactobacillus delbrueckii subsp. lactis phage LL-K, but absent from its close relative, phage LL-H. The KIS-element showed some sequence features of a transposable element: it was flanked by direct repeats of a 20 nt long sequence which was in the genome of LL-H as a target sequence. The KIS-element contained two putative ORFs. The C-terminal part of ORF333 consisted of clusters of direct repeats, capable of coding Lys/Arg-Gly-Asp motifs, which are known to be able to bind to glycoproteins. A homologous counterpart of the KIS-element was also found in the genome of prolate-headed L. delbrueckii subsp. lactis phage JCL1032, even though the phage JCL1032 is not a close relative of phage LL-K. The nucleotide sequence comparison between KIS-element and its homologous counterpart in JCL1032 showed that there have occurred several genome rearrangements at the repeat clusters.

Bacteriophages↗

PubMed1993

Characterization of a prolate-headed bacteriophage of Lactobacillus delbrueckii subsp. lactis, and its DNA homology with isometric-headed phages.

A new Lactobacillus delbrueckii subsp. lactis bacteriophage, JCL 1032, was characterized. JCL 1032 had a small, elongated prolate head, and a long non-contractile tail with cross-bars. The restriction map of JCL 1032 genome was constructed with five endonucleases. The genome was 45.8 kb in size, and it had cohesive ends (cos). Molecular masses of the phage structural proteins were also determined. JCL 1032 showed DNA homology with morphologically dissimilar, isometric-headed phages of Lb. delbrueckii (subsp. lactis and subsp. bulgaricus) when analyzed by Southern hybridization. Although in general JCL 1032 was only distantly related to isometric-headed phages, there were also a few short highly homologous (minimal homology 84%) DNA regions.

Bacteriophages↗

PubMed1989

Upstream activating sequences that are shared by two divergently transcribed operons mediate cAMP-CRP regulation of pilus-adhesin in Escherichia coli.

Transcription of the genes encoding pilus-adhesin of serotype F13 in digalactoside-binding Escherichia coli required activation by the cAMP-CRP complex. Analysis of protein-DNA interaction in vitro showed that CRP bound in a cAMP-dependent manner to a sequence located 0.2 kb upstream of the point of transcription initiation of the pilus subunit operon. The cAMP-CRP activation included, in addition to the main pilus operon, the oppositely oriented operon encoding the Papl regulatory protein. Furthermore, the auto-regulatory product of the promoter-proximal gene (papB) in the pilus subunit operon was found to stimulate the papl transcriptional unit. Thus the cAMP-CRP complex and PapB might act in concert and indirectly promote pili synthesis by stimulating expression of the Papl positive regulator. The results of trans-complementation experiments and analyses using lacZ operon fusion derivatives showed that the cAMP-CRP activation also operated directly in cis on the pilus subunit operon. The region containing the CRP binding site appeared to function as an upstream activating sequence since deletion abolished expression even when the pap regulatory proteins Papl and PapB were supplied in trans. The implications for possible mechanisms of transcriptional activation by the cAMP-CRP complex at this novel location between the two oppositely oriented operons are discussed.

Adhesins, Escherichia coli↗