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H Saedler

Publications and source records attributed to H Saedler.

18 recordsLinked to original sources
PubMed1992

Characterization of the Antirrhinum floral homeotic MADS-box gene deficiens: evidence for DNA binding and autoregulation of its persistent expression throughout flower development.

We have determined the structure of the floral homeotic deficiens (defA) gene whose mutants display sepaloid petals and carpelloid stamens, and have analysed its spatial and temporal expression pattern. In addition, several mutant alleles (morphoalleles) were studied. The results of these analyses define three functional domains of the DEF A protein and identify in the deficiens promoter a possible cis-acting binding site for a transcription factor which specifically upregulates expression of deficiens in petals and stamens. In vitro DNA binding studies show that DEF A binds to specific DNA motifs as a heterodimer, together with the protein product of the floral homeotic globosa gene, thus demonstrating that the protein encoded by deficiens is a DNA binding protein. Furthermore, Northern analysis of a temperature sensitive allele at permissive and non-permissive temperatures provides evidence for autoregulation of the persistent expression of deficiens throughout flower development. A possible mechanism of autoregulation is discussed.

Alleles↗
PubMed1992

GLOBOSA: a homeotic gene which interacts with DEFICIENS in the control of Antirrhinum floral organogenesis.

GLOBOSA (GLO) is a homeotic gene whose mutants show sepaloid petals and carpelloid stamens. The similarity of Glo mutants to those of the DEFICIENS (DEFA) gene suggests that the two genes have comparable functions in floral morphogenesis. The GLO cDNA has been cloned by virtue of its homology to the MADS-box, a conserved DNA-binding domain also contained in the DEFA gene. We have determined the structure of the wild type GLO gene as well as of several glo mutant alleles which contain transposable element insertions responsible for somatic and germinal instability of Glo mutants. Analyses of the temporal and spatial expression patterns of the DEFA and GLO genes during development of wild type flowers and in flowers of various stable and unstable defA and glo alleles indicate independent induction of DEFA and GLO transcription. In contrast, organ-specific up-regulation of the two genes in petals and stamens depends on expression of both DEFA and GLO. In vitro DNA-binding studies were used to demonstrate that the DEFA and GLO proteins specifically bind, as a heterodimer, to motifs in the promoters of both genes. A model is presented which proposes both combinatorial and cross-regulatory interactions between the DEFA and GLO genes during petal and stamen organogenesis in the second and third whorls of the flower. The function of the two genes controlling determinate growth of the floral meristem is also discussed.

Alleles↗
PubMed1979

IS2-61 and IS2-611 arise by illegitimate recombination from IS2-6.

A more stable derivative of IS2-6 has been isolated, which had lost 54 bp of the 108 bp long insert characteristic of IS2-6. This new allele of IS2, IS2-61, segregates the remaining 54 bp to yield allele IS2-611. DNA sequence analysis shows that the segregation products of IS2-6 arise by recA-independent, illegitimate recombination at 9 bp long direct sequence repetitions.

Alleles↗
PubMed1979

Development of a system useful for studying the formation of unstable alleles of IS2.

IS2-induced deletions of the gal control region were isolated in a plasmid carrying gal OP-308::IS2-7. This contains a 54 basepair long, unstable mini insertion within IS2, thus allowing constitutive expression of the gal structural genes. Deletion PPI is 11.9 kilobasepairs (kb) long and is Gal+ because it has retained the mini insertion. In PP4 7.2 kb DNA material including markers gal OP, chlD and pgl are deleted. PP4 has lost the mini insertion and is therefore Gal negative. DNA sequencing of the newly formed junction in PP4 reveals that the deletion terminates precisely at nucleotide 1 of IS2 and that no DNA sequence homology is involved in this IS2-mediated deletion formation. PPI segregates Gal- clones due to the loss of the mini insertion. One such segregant PPIS and PP4 both give only constitutive Gal+ revertants, which consist of the previously known mini insertions and also a new class of "supermini" inserts within IS2 of about 10 to 20 basepairs long. Therefore, PPIS and PP4 can be used to study various parameters involved in the formation of mini insertions.

Alleles↗
PubMed1979

Multiple integration sites for the lactose transposon Tn 951 on plasmid RP 1 and establishment of a coordinate system for Tn 951.

Various molecules generated by transposition of the lactose transposon Tn 951 from plasmid pGC1 to plasmid RP1 were examined by DNA heteroduplex and restriction endonuclease analysis. Tn 951 was found to transpose to at least eight different sites on RP 1 in both possible orientations. A coordinate system for the lactose transposon Tn 951 is constructed.

DNA Restriction Enzymes↗
PubMed1979

Integration of IS3 into IS2 generates a short sequence duplication.

The Gal+ allele IS2-43 is known to segregate Gal- clones. Among 11 Gal- segregants, one was shown to be due to the integration of IS3 into IS2-43. Precise excision of the integrated IS3 element occurred at a rate of 5 x 10(-9)/cell/generation. DNA sequence analysis revealed that the termini of the IS3 element have the relation of imperfect inverted repeats and it is now flanked by a 3bp or 4bp duplication, a size which has not been seen before with other elements.

Alleles↗
PubMed1979

IS2-43 and IS2-44: new alleles of the insertion sequence IS2 which have promoter activity.

The sequence of two new IS2 alleles with promoter activity (IS2-43 and IS2-44) is reported. The alleles are identical and are formed by a 17 bp tandem duplication in an AT-rich region of IS2. This created a new RNA polymerase binding site. A mutation was found that increased the frequency of formation of these 17 bp duplications but not of another class of duplications, the "mini-insertions". This suggested that the mechanisms of formation of the two classes of duplications are different.

Alleles↗
PubMed1979

Nucleotide sequence of the transposable DNA-element IS2.

The complete sequence of the transposable DNA element IS2 in gal OP-308:: IS2 (I) has been determined. This element is 1.327 bp long. The integrated element is flanked by a five base pair long sequence duplication. The termini of IS2 are not perfect inverted repeats, but a close approximation.

Base Sequence↗
PubMed1978

DNA sequence of the mini-insertion IS2--6 and its relation to the sequence of IS2.

In polar IS2 abolishes galactose operon expression. Operon activity is restored by a 108 base pair mini-insertion within IS2 called IS2--6. The DNA sequences of the gal operon-IS2 junction, the parental IS2 region undergoing sequence rearrangements and IS2--6 itself are reported. IS2--6 is composed of sequence intervals present in both strands of IS2.

Base Sequence↗
PubMed1978

Tn951: a new transposon carrying a lactose operon.

A new transposon, Tn951, is described, which derives from plasmid pGC1, originally isolated from Yersinia enterocolitica. Tn951 is 16.6 kb long and presumably flanked by small inverted repeats. It carries the lac genes i, z and y. This lac system is homologous to the E. coli lac operon. However, homology is restricted to 5.6 kb. The DNA sequences surrounding the lac operons on Tn951 and E. coli are nonhomologous. This leads to speculations about the origin of the E. coli lac operon itself.

Base Sequence↗
PubMed1977

Transposable genetic elements as agents of gene instability and chromosomal rearrangements.

Transposable genetic elements in prokaryotes and eukaryotes, when inserted at a given locus, can control expression of the locus and cause large scale rearrangements of adjacent DNA sequences. Striking similarities in genetic behaviour between the two groups of elements have led to the proposal of a molecular model of eukaryotic controlling elements, and to suggestions about the part such elements may play in evolution and differentiation.

Base Sequence↗
PubMed1975

IS1 is involved in deletion formation in the gal region of E. coli K12.

The DNA sequence IS1, which is 800 pairs long, has been shown to integrate into various bacterial and phage operons. The presence of this DNA sequence in the gal operon of E. coli K12 leads to an 30-2000 fold increase in deletion formation in the gal region as compared to wildtype. This high frequency of deletion formation is specific for IS1 and is independent of the cellular recA function. While the frequency of reversion of gal::IS1 mutations, which also is independent of recA, is not affected by the growth temperature of the cells, the formation of deletions in the gal::IS1 system is strongly dependent on the temperature of growth. Mapping experiments showed that one endpoint of the deletions in most cases is at the site of the IS1 mutation and the second endpoint seems to be at various but preferred sites. The formation of the different classes of delections observed is affected differently by the growth temperature of the cells. A model to account for these results is presented.

Chromosome Aberrations↗
PubMed1975

Electron microscope heteroduplex studies of sequence relations among bacterial plasmids: identification and mapping of the insertion sequences IS1 and IS2 in F and R plasmids.

Heteroduplex experiments between the plasmid R6 and one strand of the deoxyribonucleic acid (DNA) of a lambda phage carrying the insertion sequence IS1 show that IS1 occurs on R6 at the two previously mapped junctions of resistance transfer factor (RTF) DNA with R-determinant DNA. From previous heteroduplex experiments, it then follows that IS1 occurs at the same junctions in R6-5, R100-1, and R1 plasmids. Heteroduplex experiments with the DNA from a lambda phage carrying the insertion sequence IS2 show that one copy of IS2 occurs in R6, R6-5, and R100-1 (but not R1) at a point within the RTF with coordinates 67.5 TO 68.9 kilobase units (kb). In an accompanying paper, Ptashne and Cohen (1975) show that the insertion sequence IS3 occurs on R6 and R6-5. R100-25, a traC mutant, differs from its parent R100-1 only in that it contains an additional copy of IS1 inserted within the tra gene region of 82.1 kb. R100-31, atraX, TC-s mutant of R100-1, is deleted in R100-1 sequences starting at one of the IS3 termini (46.9 kb) and extending with RTF to 61.0 kb. Heteroduplex studies of F plasmids with the DNA of a lambda phage bearing insertion sequence IS2 show that the sequence of F with coordinates 16.3-17.6F is IS2. The occurrence of IS1 at the two junctions of R-determinant DNA and RTF DNA in R plasmids provides a structural basis to explain the mechanism of the previously observed formation of molecules containing one RTF unit and several tandem copies of the R-determinant unit, when R plasmids in Proteus mirabilis are grown in the presence of antibiotics, and the segregation of an R plasmid into an RTF unit and an R-determinant unit. In general, correlation of our results with previous studies shows that insertion sequences play a role in a variety of F- and R-related intra- and intermolecular recombination phenomena.

Base Sequence↗