|
|
The way State Agricultural Biotechnology Centre (SABC) Honours student Derek Bartlem and PostDoctoral Fellow Dr Tatjana Heinrich explained their current research it sounded relatively simple and straightforward.
 Just take one specific, minuscule amount of genetic material, which has been extracted from a North-West Pacific Ocean jellyfish, insert the gene into plant cells and regrow whole plants in the SABC laboratories at Murdoch University.
Unfortunately it isn't as easy as it sounds. It's taken Derek and Tatjana, working in a team led by SABC Director Professor Mike Jones, more than eight months to accomplish the transfer.
Their ground-breaking work, which places them at the leading edge of this kind of science in Australia, has the potential to be of great benefit to agricultural research in the State.
Getting plants to produce the protein  Green Fluorescent Protein (GFP) within their own structure has enabled the SABC researchers to view living plant cells for the first time without having to destroy the very tissue they are trying to investigate.
In the past, scientists monitoring the spread of plant diseases have had to section genetically-modified plant tissue and stain it with dyes which effectively kill the tissue, before examining expression of introduced genes.
Using GFP as a 'fluorescent label', they need do no more than place transgenic plant tissues under ultra violet light or examine them using a Confocal Laser Scanning Microscope (CLSM), leaving the plant tissues alive and well, and ready to be examined on a continual basis.
|
|
GFP is normally produced by the jellyfish Aequorea victoria which, when agitated, emits a bright green flash. Presumably a defence mechanism to blind attackers, the fluorescence is often observed in the wake of ships passing through ocean waters containing the jellyfish.
Scientists researching the GFP in jellyfish soon realised that if they could isolate the GFP gene and fuse its DNA coding sequence to those of other proteins whose expression or location is of interest, they would have an immensely valuable research tool functioning as a 'reporter' of gene expression in vivo over time, and an efficient selectable marker suitable for automated research procedures. This would effectively do away with the need to use exogenous agents dyes to stain physically-sectioned tissues.
Living plant tissue could instead be 'sectioned' optically using the CLSM, to allow analysis of cellular and subcellular detail.
Using GFP in plants, fluorescent-imaging microscopy can be used to track the expression and location of proteins and other microstructures within organisms as diverse as viruses and nematodes such as those with a destructive effect on agricultural crops.
The first research of this kind was carried out by a team led by Dr Jim Haseloff at the MRC Laboratory for Molecular Biology at Cambridge, in England.
On hearing of the Cambridge research, the SABC scientists soon recognised its potential as a research tool in the investigation of Western Australian agricultural plant diseases.
The first plant genetically engineered to contain GFP at Murdoch University was tobacco (Nicotiana tabacum), which was chosen simply because it is an easy plant into which new genes can be introduced.
Using a CLSM, the SABC research team confirmed the success of its initial experiments by obtaining images of the GFP within their transgenic tobacco plants. Their research has since been further developed to involve a brassica-type weed called Arabidopsis thaliana another 'model plant' species.
The introduction of GFP from the jellyfish into plants is achieved through a process called plant transformation. A DNA 'plasmid' containing the GFP gene is made, then put into a soil bacterium that is used as a vector to transfer that gene into cells within a small amount of plant tissue. A series of complex steps follow, involving the regeneration of a whole plant from the small amount of localised cells, which ultimately leads to the emergence of a new, completely transformed plant whose seeds have the potential to create future plants which automatically contain GFP.
Professor Jones said the Murdoch team has been able to produce the green fluorescent protein in every cell within the new transgenic plant.
"But we can also link different instructions to the GFP gene and direct the plant to produce the protein only in specific parts of the plant," he said.
"This will be especially important for research with Arabidopsis thaliana and the study of root-attacking nematode pests.
"By using plants which produce GFP only in certain root tissues, the team will be able to find out exactly from which cells the nematode feeds and to follow up the fate of these cells throughout the life cycle of the parasite."
There are no current plans to develop agricultural plants which contain GFP, but rather to use the information gathered through its use to create nematode-resistant plants.
By finding out how the nematode invades plant defences and how it changes the plant cells to produce food for the parasite which is the reason why nematode-infected plants show stunted growth and reduced yield the research team hopes to be able to create new forms of resistance.
|