Because of their small genome size, genetic diversity and ease of mutation and selection, bacteria are an important source of useful genes for transfer into plant cells. Several bacterial genes are well established as reporter genes for use in plant molecular research and others are under investigation as novel for useful agronomic traits such as disease resistance. Two of the primary needs for use of bacterial genes in plant cells are plant gene control sequences directing appropriate patterns of expression and efficient assays for the novel gene product in plant cells. The work in this thesis was undertaken to contribute to both of these aspects. Bacterial chitinases have the potential to increase disease resistance if expressed in plant cells, but this research has been hindered by difficulty in measuring the novel gene product against the background of plant chitinases. In work to overcome this limitation a bacterial exo-chitinase gene fused to the 35SCaMV promoter element was transformed into plant tumour cells. The level of expression directed by this construct was quantified using a substrate that was preferentially hydrolysed by bacterial exo-chitinase. Tumours transformed with the chitinase construct hydrolysed the specific substrate with a rate 3 fold that of control tumours. Using this specific exo-chitinase assay the average level of chitinase transgene expression in pooled tumour cells directed by the 35SCaMV promoter element was 0.1 % of total cellular protein. A second part of the work for the improved detection of bacterial gene products in transgenic plants was undertaken to provide a safe, economical and convenient assay for the expression of the neo reporter gene in plant tissues. An enzyme linked immunosorbant assay for neomycin phosphotransferase gene product (NPTII) was optimized. The assay had statistically defined lower detection limit of 50pg NPTII/mg of total cellular protein in tissue cultured plants, and was used to detect up to 4ng NPTII/mg total cellular protein in plants transformed with a nopaline synthase promoter (NOP)-neo construct. This sensitive, and readily quantifiable alternative to the established radioactive NPTII assay proved particularly useful for the large scale screening and direct quantification of NPTII in plant tissues, required in subsequent plant promoter tagging experiments. Several approaches to the isolation of plant promoters are available, including differential hybridization, cloning genomic fragments into promoter probe vectors and tagging by introduced promoterless reporter genes. Each technique has potential advantages and all have technical limitations. In work to improve the feasibility of cloning into promoter probe vectors for the isolation and detection of plant promoter elements, an electroporation protocol was developed for gene transfer into Agrobacterium sp which increased the frequency the transformation frequency of Agrobacterium sp from 1 x 103 to 1 x 108 in some strains. Agrobacterium tumefaciens T-DNA mediated plant promoter tagging was investigated. Using the optimised NPTII ELISA assay, neo expression levels were also quantified in Nicotiana tabacum that was transformed with an Agrobacterium tumefaciens T-DNA construct carrying a right border linked promoterless neo gene. Approximately 1 in 10 promoterless neo gene integrations were expressed to levels that initially afforded resistance to kanamycin. Transgenic plants carrying right border linked promoterless neo T-DNA integrations expressed neo to levels between 50 and 500 pg NPTII/mg protein in vegetative plant tissues. All transformants examined directed neo expression levels between 5 and 10 times lower than control plants transformed with a NOP-neo construct. Two modifications of a Single Sequence Specific Polymerase Chain Reaction (SSSPCR) Strategy were investigated for isolating plant genomic elements associated with right border linked promoterless neo T-DNA integrations. Southern hybridization of neo specific gene sequences to amplification products revealed that neo containing sequence was generated. The size of the neo specific amplicon suggested that plant genomic DNA associated with the neo insertion had also been amplified. Sequence data from cloned SSSPCR fragments revealed that non-specific amplification resulting from undesirable template ligation products and non-specific priming contributed to the large amounts of amplification product that did not contain neo gene sequence. Strong hybridization indicated that up to ng quantities of specific product had been amplified and suggested that an SSSPCR fragment library should readily produce an neo containing clone. However the cloning efficiency of SSSPCR fragments was not high enough to permit estimation of the frequency at which an neo bearing clone would be obtained. Additional work on amplification strategies and the development of an efficient cloning procedure for SSSPCR generated fragments will be required to make this approach reliable for plant promoter rescue.