Transformed petunia, tobacco, and tomato plants have been produced by means of a novel leaf disk transformation-regeneration method. Surface-sterilized leaf disks were inoculated with an Agrobacter...

A simple and general method for transferring genes into plants

TELOMERES DEFINED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 579 TELOMERE FUNCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 580 SEQUENCE AND STRUCTURE OF TELOMERES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 581 SOLUTIONS FOR REPLICATION OF DNA TERMINI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 586 STRUCTURE OF SUBTELOMERIC REGIONS.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 589 FORMA TION OF TELOMERES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . .. 591 PROTEINS THAT INTERACT WITH TELOMERES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 594 ARE TELOMERES REALLY ESSENTIAL? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 597 FUTURE PROSPECTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 598

Structure and function of telomeres

Molecular genetics approaches have been used to identify and characterize cis-acting DNA sequences required for eukaryotic gene regulation. These sequences are modular in nature, consisting of arrays of short (10- to 12-base pair) recognition elements that interact with specific transcription factors. Some transcription factors have been extensively purified and the corresponding genes have been cloned, but the mechanisms by which they promote transcription are not yet understood. Positive and negative regulatory elements that function only in specific cell types or in response to extracellular inducers have been identified. A number of cases of inducible and tissue-specific gene expression involve the activation of preexisting transcription factors, rather than the synthesis of new proteins. This activation may involve covalent modification of the protein or an allosteric change in its structure. The modification of regulatory proteins may play a central role in the mechanisms of eukaryotic gene regulation.

https://science.sciencemag.org/content/sci/236/4806/1237.full.pdf

Regulation of inducible and tissue-specific gene expression

https://www.cell.com/cell/pdf/0092-8674(90)90141-Z.pdf

Position Effect at S. cerevisiae Telomeres: Reversible Repression of Pol II Transcription

A single P element insert in Drosophila melanogaster, called P[ry+ delta 2-3](99B), is described that caused mobilization of other elements at unusually high frequencies, yet is itself remarkably stable. Its transposase activity is higher than that of an entire P strain, but it rarely undergoes internal deletion, excision or transposition. This element was constructed by F. Laski, D. Rio and G. Rubin for other purposes, but we have found it to be useful for experiments involving P elements. We demonstrate that together with a chromosome bearing numerous nonautonomous elements it can be used for P element mutagenesis. It can also substitute efficiently for "helper" plasmids in P element mediated transformation, and can be used to move transformed elements around the genome.

/pdf/a-stable-genomic-source-of-p-element-transposase-in-37qqowy5kn.pdf

A stable genomic source of P element transposase in Drosophila melanogaster.

Transformation of white locus DNA in Drosophila: dosage compensation, zeste interaction, and position effects

The white gene of Drosophila is expressed normally when introduced at many different sites in the genome by P-element-mediated DNA transformation, but is expressed abnormally when inserted at two particular genomic positions It is now demonstrated that the mutant expression in these two cases is caused by the surrounding chromosomal region into which the white gene has been inserted The white gene could be moved from these two positions, where it confers a mutant phenotype, to other positions in the genome where it confers a wild-type phenotype However, flies in which white has been moved to one new location have an unusual mosaic phenotype

Effects of genomic position on the expression of transduced copies of the white gene of Drosophila.

The white gene of Drosophila is required for the pigmentation of the eyes, ocelli, Malpighian tubules and testis sheath. We have examined the regulation of white expression in germ line transformants that carry the mRNA-coding sequences of white flanked by varying amounts of the sequences normally located adjacent to them. A segment with as little as 1.9 kb of 5'- and 2.1 kb of 3'-flanking DNA was expressed to give essentially wild-type pigmentation in all of these tissues and interacted in trans with the zeste-1 allele. In contrast, transformants having segments with 1.1 kb of 5'-flanking DNA had reduced levels of pigment in their eyes, no detectable pigment in their testes and did not interact with zeste-1. The eyes, Malpighian tubules and ocelli of transformants with as little as 0.4 kb of 5'-flanking DNA were pigmented and the eye pigmentation exhibited dosage compensation. We conclude that there are sequence elements present in the region from 1.1 to 1.9 kb upstream from the 5' end of the white transcript which are required for expression in the testes and interaction of white and zeste-1. The same or other elements in this region appear to augment the pigmentation of the eye.

https://www.embopress.org/doi/pdf/10.1002/j.1460-2075.1985.tb04108.x

Tulle Hazelrigg

Papers

Transformation of white locus DNA in Drosophila: dosage compensation, zeste interaction, and position effects

Effects of genomic position on the expression of transduced copies of the white gene of Drosophila.

Separable cis-acting control elements for expression of the white gene of Drosophila.

Germ line specificity of P-element transposition and some novel patterns of expression of transduced copies of the white gene.

The Use of Transposable Elements as Vectors for Gene Transfer in Drosophila