George C. Allen

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We have previously shown that yeast scaffold attachment regions (SARs) flanking a chimeric beta-glucuronidase (GUS) reporter gene increased per-copy expression levels by 24-fold in tobacco suspension cell lines stably transformed by microprojectile bombardment. In this study, we examined the effect of a DNA fragment originally identified in a tobacco(More)
The RB7 matrix attachment region (MAR), when flanking a uidA (GUS) reporter gene, has been previously shown to increase uidA gene expression by 60-fold in stably transformed tobacco suspension cell lines. We have now used the same co-transformation procedure to determine the effect of flanking MARs on uidA gene expression in tobacco plants. The neomycin(More)
Matrix attachment regions (MARs) are operationally defined as DNA elements that bind specifically to the nuclear matrix in vitro. It is possible, although unproven, that they also mediate binding of chromatin to the nuclear matrix in vivo and alter the topology of the genome in interphase nuclei. When MARs are positioned on either side of a transgene their(More)
DNA replication programs have been studied extensively in yeast and animal systems, where they have been shown to correlate with gene expression and certain epigenetic modifications. Despite the conservation of core DNA replication proteins, little is known about replication programs in plants. We used flow cytometry and tiling microarrays to profile DNA(More)
Matrix attachment regions (MARs) can be operationally defined as DNA fragments that bind to the nuclear matrix. We have created a library of randomly obtained MARs from tobacco (Nicotiana tobacum) by cloning DNA fragments that co-isolate with nuclear matrixes prepared by a method involving lithium diiodosalicylate. The interactions of several of the cloned(More)
Genetic engineering of commercially important crops has become routine in many laboratories. However, the inability to predict where a transgene will integrate and to efficiently select plants with stable levels of transgenic expression remains a limitation of this technology. Fluorescence in situ hybridization (FISH) is a powerful technique that can be(More)
The sugar alcohol mannitol is a carbohydrate with well-documented roles in both metabolism and osmoprotection in plants and fungi. In addition, however, mannitol is an antioxidant, and current research suggests that pathogenic fungi can secrete mannitol into the plant’s extracellular spaces during infection to suppress reactive oxygen-mediated host(More)
Spatiotemporal patterns of DNA replication have been described for yeast and many types of cultured animal cells, frequently after cell cycle arrest to aid in synchronization. However, patterns of DNA replication in nuclei from plants or naturally developing organs remain largely uncharacterized. Here we report findings from 3D quantitative analysis of DNA(More)
In vitro manipulations of cotton often require high-quality sterile seedlings as a source of hypocotyl and cotyledon explants for initiation of embryogenic cultures or embryo apexes for shoot production. Unfortunately, in vitro seed germination is often hindered if cotton seeds were collected from the open field and stored under improper conditions. In our(More)
The duration of the DNA synthesis stage (S phase) of the cell cycle is fundamental in our understanding of cell cycle kinetics, cell proliferation, and DNA replication timing programs. Most S-phase duration estimates that exist for plants are based on indirect measurements. We present a method for directly estimating S-phase duration by pulse-labeling root(More)