Life Sciences Commons^™

Efficient Gene Transfer In C.Elegans: Extrachromosomal Maintenance And Integration Of Transforming Sequences, Craig Mello, James Cramer, Dan Stinchcomb, Victor Ambros

Victor R. Ambros

We describe a dominant behavioral marker, rol-6(su-1006), and an efficient microinjection procedure which facilitate the recovery of Caenorhabditis elegans transformants. We use these tools to study the mechanism of C.elegans DNA transformation. By injecting mixtures of genetically marked DNA molecules, we show that large extrachromosomal arrays assemble directly from the injected molecules and that homologous recombination drives array assembly. Appropriately placed double-strand breaks stimulated homologous recombination during array formation. Our data indicate that the size of the assembled transgenic structures determines whether or not they will be maintained extrachromosomally or lost. We show that low copy number extrachromosomal transformation can …

The Electrical Response Of Maize To Auxin, Hubert Felle, Winfried Peters, Klaus Palme

Winfried S. Peters

Control Of Apoplast Ph In Corn Coleoptile Segments. I: The Endogenous Regulation Of Cell Wall Ph, Winfried Peters, Hubert Felle

Winfried S. Peters

Control Of Apoplast Ph In Corn Coleoptile Segments. Ii: The Effects Of Various Auxins And Auxin Analogues, Winfried Peters, Hubert Felle

Winfried S. Peters

Alternative Temporal Control Systems For Hypodermal Cell Differentiation In Caenorhabditis Elegans, Zhongchi Liu, Victor Ambros

Victor R. Ambros

Beginning of article: In certain multicellular organisms, genetic regulatory systems that specify the timing of cell division, differentiation and morpho-genesis must accommodate environmental and physiological contingencies that perturb or arrest development. For example, Caenorhabditis elegans can either develop continuously through four larval stages (L1–L4) or arrest indefinitely as a 'dauer larva' at the second larval (L2) moult, and later resume L3 and L4 development. At the larva-to-adult (L4) moult of both con-tinuous and 'post-dauer' development, hypodermal cells switch (the 'L/A switch') from a proliferating state to the terminally differentiated state. Four temporal regulators, lin-4, lin-14, lin-28 and lin-29, have been …

Molecular Cloning Of Lin-29, A Heterochronic Gene Required For The Differentiation Of Hypodermal Cells And The Cessation Of Molting In C.Elegans, A. Papp, A. Rougvie, Victor Ambros

Victor R. Ambros

The lin-29 gene product of C.elegans activates a temporal developmental switch for hypodermal cells. Loss-of-function lin-29 mutations result in worms that fail to execute a stage-specific pattern of hypodermal differentiation that includes exist from the cell cycle, repression of larval cuticle genes, activation of adult cuticle genes, and the cessation of molting. Combined genetic and physical mapping of restriction fragment length polymorphisms (RFLPs) was used to identify the lin-29 locus. A probe from the insertion site of a Tc1 (maP1), closely linked and to the left of lin-29 on the genetic map, was used to identify a large set of …

Thermodynamics Of Charged Oligopeptide Nucleic Acid Interactions, David Mascotti, T. Lohman

David P. Mascotti

No abstract provided.

Changes In Hydraulic Conductivity And Anatomy Caused By Drying And Rewetting Roots Of Agave Deserti (Agavaceae), Gretchen North, P. Nobel

Gretchen North

Concurrent determinations of changes in hydraulic conductivity and tissue anatomy were made for roots of Agave deserti excised during drying and following rewetting in soil. At 30 d of drought, hydraulic conductivity had declined less than twofold for older nodal roots, tenfold for young nodal roots, and more than 20-fold for lateral roots ("rain roots" occurring as branches on the nodal roots). These decreases were consistent with increases in cortical lacunae caused by cell shrinkage and collapse. Similarly, reduction of lacunae in response to rewetting after 7 d of drought corresponded to levels of recovery in hydraulic conductivity, with young …