Ubiquitous RNA-dependent RNA polymerase and gene silencing

The discovery of a ubiquitous RNA-dependent RNA polymerase raises new questions about small RNA silencing mechanisms

Meiotic behavior of small chromosomes in maize

The typical behavior of chromosomes in meiosis is that homologous pairs synapse, recombine, and then separate at anaphase I. At anaphase II, sister chromatids separate. However, studies of small chromosomes in maize derived from a variety of sources typically have failure of sister chromatid cohesion at anaphase I. This failure occurs whether there is pairing of two copies of a minichromosome or not. These characteristics have implications for managing the transmission of the first generation artificial chromosomes in plants. Procedures to address these issues of minichromosomes are discussed

Drosophila KDM2 is a H3K4me3 demethylase regulating nucleolar organization

<p>Abstract</p> <p>Background</p> <p>CG11033 (dKDM2) is the <it>Drosophila </it>homolog of the gene KDM2B. dKDM2 has been known to possess histone lysine demethylase activity towards H3K36me2 in cell lines and it regulates H2A ubiquitination. The human homolog of the gene has dual activity towards H3K36me2 as well as H3K4me3, and plays an important role in cellular senescence.</p> <p>Findings</p> <p>We have used transgenic flies bearing an RNAi construct for the dKDM2 gene. The knockdown of dKDM2 gene was performed by crossing UAS-RNAi-dKDM2 flies with actin-Gal4 flies. Western blots of acid extracted histones and immunofluoresence analysis of polytene chromosome showed the activity of the enzyme dKDM2 to be specific for H3K4me3 in adult flies. Immunofluoresence analysis of polytene chromosome also revealed the presence of multiple nucleoli in RNAi knockdown mutants of dKDM2 and decreased H3-acetylation marks associated with active transcription.</p> <p>Conclusion</p> <p>Our findings indicate that dKDM2 is a histone lysine demethylase with specificity for H3K4me3 and regulates nucleolar organization.</p

Using Fluorescence in situ hybridization to study maize lines genetically predicted to have chromosomal abnormalities [abstract]

Abstract only availableSince the 1960s, genetic evidence has indicated chromosome damage and nondisjunction in lines of maize containing knob heterochromatin-bearing chromosomes and at least two B chromosomes. However, at that time researchers lacked the technology to visualize these occurrences. Now, using Fluorescence in situ Hybridization to "paint" and photograph the chromosomes, it is possible to accurately karyotype and identify broken, missing, or extra chromosomes. A line with a very large number of heterochromatic knobs had been crossed with another line containing supernumerary B chromosomes. This F1 hybrid that had been self pollinated (B73+B/K10) was chosen for study by the FISH method because it contains both knobs and B chromosomes, as well as exhibiting abnormalities such as irregular rows, ovule abortion, and defective kernels. This material combined a high knob number with B chromosomes and exhibited properties suggestive of chromosome breakage or nondisjunction. Metaphase spreads from the root tips were prepared and hybridized to fluorescent probes. Spreads were observed using fluorescence microscopy. The majority of the plants studied possessed the normal content of 20 A chromosomes plus varying numbers of B chromosomes. One individual was found with 21 chromosomes that might have resulted from nondisjunction. No chromosomal breakage was evident in this background. FISH proved to be a powerful cytogenetic tool in observing these plants; however, further research on this topic is needed to provide insight into the cause of the genetic abnormalities

Construction and applications of engineered minichromosomes in plants

The use of genetically modified crops is constantly finding new areas of application, including the production of compounds with therapeutic value. Current technology for producing transgenic crops relies on random integrations that can have variable expression and could potentially disrupt the endogenous genes. Also combining multiple transgenes requires a lengthy crossing scheme and can bring along linked genes from one variety into another. The current invention developed by researchers at the University of Missouri is a technology that will allow continued addition of transgenes as the need arises in the future using engineered plant minichromosomes. Artificial chromosome platforms in maize were produced by telomere-mediated truncation while simultaneously adding sequences that will permit amendments to the chromosome indefinitely. Such engineered minichromosomes have the potential to be used as a vector for efficient stacking of multiple genes for insect, bacterial and fungal resistances together with herbicide tolerance and crop quality traits unlinked to endogenous genes in a circumstance that would foster faithful expression. The collection of transgenes on minichromosomes might be combined with haploid breeding techniques to facilitate their transfer among diverse lines of a crop. A toolkit of lines that will permit additions and subtractions of genes from engineered minichromosomes is being assembled. Because of the near universality of the telomere sequence in the plant kingdom, engineered minichromosomes should be able to be produced easily in most plant species by this technique. Potential Areas of Applications: * Stack multiple transgenes on an independent chromosome with potentially no limit to number. * Facilitate transfer of transgenes into different varieties of a crop species by combining them with haploid breeding procedures