Promoter activity and expression of sequences from Ti-plasmid stably maintained in mammalian cells

An alternative method of promoter assessment by confocal laser scanning microscopy

A rapid and useful method of promoter activity analysis using techniques of confocal laser scanning microscopy (CLSM) is described in the present study. The activities of some pararetroviral promoters such as CaMV35S (Cauliflower mosaic virus), FMVSgt3 (Figwort mosaic virus sub-genomic transcript) and MMVFLt12 (Mirabilis mosaic virus full-length transcript) coupled to GFP (green fluorescent protein) and GUS (beta-glucuronidase) reporter genes were determined simultaneously by the CLSM technique and other available conventional methods for reporter gene assay based on relevant biochemical and molecular approaches. Consistent and comparable results obtained by CLSM as well as by other conventional assay methods confirm the effectiveness of the CLSM approach for assessment of promoter activity. Hence the CLSM method can be suggested as an alternative way for promoter analysis on the basis of high throughput.

Transient expression in mammalian cells of transgenes transcribed from theCauliflower mosaic virus35S promoter

Gene constructs containing the Cauliflower mosaic virus (CaMV) 35S promoter and a sequence coding either for a green fluorescent protein (GFP) or for firefly luciferase were transfected into Chinese hamster ovary (CHO) cells. Both reporter genes were expressed to significant levels. The 35S promoter was 40 times less active than the human eF1 alpha promoter, which is known to be one of the most potent promoters in mammalian cells. The 35S promoter must therefore be considered to be a promoter of significant potency in mammalian cells. RT-PCR analysis suggested that transcription initiation in CHO cells occurred between the TATA box and the transcription start site of the 35S promoter that function in plant cells. Further analysis by 5'RACE confirmed that transcription was initiated in CHO cells at different sites located essentially between the TATA box and the plant transcription start site, showing that 35S promoter activity in animal cells is due to the presence of promoter elements that are functional in mammalian cells, but that are not those used in plants. The data reported here raise the possibility that genes controlled by the 35S promoter, which is commonly used in transgenic plants, have the potential for expression in animal cells.

The Chlorella virus adenine methyltransferase gene promoter is a strong promoter in plants

An upstream region isolated from a eukaryotic algal virus adenine methyltransferase gene was tested for promoter function in plants. Fusion of this region to the chloramphenicol acetyltransferase reporter gene resulted in significantly higher expression than fusion with the cauliflower mosaic virus 35S promoter. Strong levels of expression were also found in electroporated monocot plant cells. The promoter activity in transgenic tobacco plants showed tissue-specific expression. Leaves had the highest expression followed by stems and flowers. The promoter activity was not detected in root tissue. Environmental cues, such as light, and the phytohormones auxin and cytokinines had no effect on the promoter's expression. This promoter might be utilized to achieve high levels of expression of introduced genes in higher plants.

Strategies in pathogenesis: mechanistic specificity in the detection of generic signals

The virulence genes of the plant pathogen Agrobacterium tumefaciens are induced by more than 40 low-molecular-weight phenolic compounds. The prevailing opinion is that (i) wound-derived phenols produced on breach of the integrity of the cell wall act as the initiating signal in a series of events which results in host cell transformation, and (ii) a classical membrane receptor, putatively VirA, is responsible for the recognition of all such phenolic inducers. Here, we argue that the discovery of the subset of inducers that are relatives of the dehydrodiconiferyl alcohol glucoside (DCG) growth factors redirects our attention to work on the plant wound as a site of cell division, and suggests that we further explore the implications of early work on the relationship between transformation efficiency and the status of the cell cycle of the host. In addition, we argue that the significant structural diversity allowed in the para position of the phenol ring of inducers suggests that a receptor-ligand interaction based solely on structural recognition is insufficient, but that recognition followed by a specific proton transfer event may be sufficient to explain vir induction activity. Hence, the specificity of the response of A. tumefaciens may be a consequence of the features required for a chemical reaction to occur on the receptor surface. Finally, we review affinity labelling studies which exploit this phenol detection mechanism and which provide evidence that the phenol receptor may be other than VirA, the sensory kinase of the two component regulatory system implicated in Agrobacterium virulence.(ABSTRACT TRUNCATED AT 250 WORDS)