ANNUAL SYMPOSIUM

Australia's science future 3-4 May 2000
Full listing of papers

Dr Frank Gubler received a PhD from the University of New South Wales for work on protein secretion in plant cells. After postdoctoral work on the cell biology of the dieback fungus (Phytophthera cinnamomi) at the Research School of Biological Sciences, Australian National University, he joined CSIRO in 1991. His work at CSIRO and the CRC for Plant Science has focused on hormonal control of gene expression in cereal grains, particularly in germination processes.

 

Symposium themes - Genetic engineering of plants and animals

Exploring the plant genome
by Frank Gubler
f.gubler@pi.csiro.au

Abstract
The whole genome for Arabidopsis, a mustard-like weed, will be sequenced by 2000, and the genome of the model cereal, rice, will be sequenced by 2004. Current estimates indicate that each genome contains between 20,000 and 30,000 genes, of which many have an unknown function. The challenge for plant biologists will be to explore these newly discovered genes and try to understand their roles in plant growth and development. This global approach to gene isolation and function is called genomics. New tools are currently being developed to help us identify the function of these genes. Gene chips containing up to 20,000 genes will allow researchers to monitor the expression of all genes simultaneously during various stages in a plant’s life. The Gene Machine will give researchers access to mutants, which help them identify the function of any particular gene.

As a result of these new approaches we will be able to identify key genes that regulate germination and seedling vigor, flowering, drought tolerance and many other aspects of plant development. In the near future, breeding programs will use the knowledge we have gained from genomics to improve the agronomic performance of many crop plants.

Genomics is going to revolutionise plant biology over the next decade. It will provide vast amounts of data on plant characteristics and how to use them better.

What controls plant growth and development? When and where are genes expressed? What is their function?

Gene chips measure the expression of every gene at once. Microarrays of up to 20,000 gene markers on a microscope slide show a change in colour when a gene is turned on. These gene chips allow us to look at gene expression in different parts of plants and at different stages in their lives.

The whole genome of Arabidopsis, a mustard-like weed, will be sequenced this year. But we do not know the function of most of its genes. That presents us with a challenge. We will use arrays to find when genes are expressed in leaves, seeds or roots.

We can then go into bulk production of gene knockout mutants, each missing a single gene, to see what the effect of that gene is. It may affect the size of the plant, its flowering or some other characteristic.

With another technique we can zoom into the roots or leaves of a plant to see where the gene is expressed.

These technologies mean that the expression and function of the 20,000 plant genes will be confirmed. This will allow us to investigate the complex networks that regulate plant growth and development. In these networks environmental signals are perceived by receptors in the plant, turning on regulators. The regulators turn on target genes which control the appropriate response.

Waterlogging in plants such as cotton can reduce the amount of oxygen available to the roots, reducing growth. CSIRO has used a gene chip to identify the genes expressed in response to low oxygen some are turned on, others are turned off. This way we will learn how to engineer plants which are flood tolerant.

How does a plant know when to flower? We have looked at Arabidopsis mutants to find the genes controlling flowering time. There are three factors temperature, stage of development and day length. By looking at the genes affected in late and early flowering mutants we may be able to manipulate the flowering time in plants.

Genomics will transform knowledge of how to regulate plant growth and development and deliver new genes to breeding programs for better agricultural performance.

Session discussion

Who is going to benefit from this technology? How can the benefits be passed on to everyone in the world?

Carolyn Schultz. Whoever is paying for the research controls it. We have to rely on foundations that do work to benefit developing nations.

Peter Rathjen. We have to make sure there is adequate competition so one company cannot tie up the technology. Patent control is the key thing. We need resources for breakthroughs and to stay at the table.

Are edible vaccines broken down in the gut?

Carolyn Schultz. DNA is broken down into building blocks but this is not always so with proteins. The vaccines are fused with disabled cholera toxin to make them stable, so that they are taken up through the gut lining.

Are we going to get hydroponic meat?

Peter Rathjen. There is an important technical barrier to that. We can multiply cells but we can’t make them organise into their final form. Scientists in the USA are making organ and tissue scaffolds. Meat may be possible in the next few decades.

What are the risk factors of genetic modification?

Carolyn Schultz. The risk factors that have been reported such as increased herbicide resistance would happen with existing methods. Other risks are exaggerated such as the suggestion that modified corn would kill monarch butterflies. The basis of this report was due to poorly designed experiments. We need case by case field testing and assessment of risks.

Frank Gubler. Modified cotton pollen cannot be transferred to native cotton.

What is the potential and the risk of the transfer of stem cells or differentiated cells descended from stem cells?

Peter Rathjen. Embryonic stem cells would not be transplanted as they do cause cancers. Their immortal potential is lost after differentiation. We can control and eliminate carcinogenic effects. We are learning how to do it.

Is there more known about reprogramming cells?

Peter Rathjen. One possibility is to inject a nucleus into an embryo and then isolate the stem cells. With humans this is ethically fraught. But it may be possible to directly reprogram from an adult cell to a stem cell without going through the embryo.

Dolly was not identical to her mother, she was prematurely aged. When will we truly clone?

Peter Rathjen. I doubt we will want to truly clone. Mitochondrial DNA won’t be important for the immune system. Genetic modifications can be made in the nucleus. I’m not sure of the advantages of doing it to mitochondria.

This work depends on public perceptions. We are not doing well at informing the public. In terms of regulation, the new gene technology Bill gives the public less access than they have now. How do we turn public opinion against the bad but not the good?

Carolyn Schultz. I don’t know that you can do a lot more. You have to get the benefits to the consumers, not the companies. It is not going to happen in a hurry.

Frank Gubler. People don’t object to genetically modified medicines.

Peter Rathjen. The Swiss, in a referendum, almost banned genetic engineering. There is little known about genes. Biology is not studied extensively in schools education programs have to be improved.

What causes side effects?

Peter Rathjen. There is not sufficient hard data. This has to be solved before the technology is applied.

Frank Gubler. The testing of plants, especially foods, needs to be rigorous.

 

The public has a strong input into legislation. We need a new breed of scientists to educate the public.

Why are people worried about the ethical consequences of gene technology?

Carolyn Schultz. That does not apply so much to plants. The main problem is a poor understanding of what a gene is. It is hard to see big ethical problems, people are more concerned about environmental issues.

Peter Rathjen. The destruction of human embryos raises ethical problems. Ethical concerns are often based on ignorance; that will pass. People may apply technology in all sorts of ways. Mad people will do mad things. We can’t design legislation against stupid uses.

Scientists explaining is not adequate. We must improve science teaching.

Stem cells are found throughout the human brain. We could gain neurons as we age. In Parkinson’s disease we may be able to reproduce, migrate and connect cells to remove the condition. There are great prospects for stem cell work.

Will the beta-carotene in golden rice by inactivated by heat (cooking)?

Carolyn Schultz. We boil carrots and still get the benefits.

Some dangers are associated with biotechnology. One concern is the vectors (viruses and bacteria) used in cloning and the introduction of genes into cells. Another is that inserting genes into positions we cannot predict may modify the expression of some genes, producing effects that we cannot predict.

Carolyn Schultz. There is a very small risk of transfer of antibiotic resistance. Resistance genes are already very abundant in the bacteria or our gut and the soil. New markers are being developed.

Peter Rathjen. We no longer use viral and bacterial vectors in animals. We don’t leave behind things we don’t want.

Frank Gubler. In plants we have moved away from antibiotic-resistant genes. We just use the genes we want.

How many genes does it take to modify cattle hooves so that they do less damage to our environment?

Peter Rathjen. I can’t guess.

There is a need for early education about science, using programs such as the Academy’s Primary Investigations. Primary science is very important.

There are limitations to how much you can educate the general public. Some people just regard certain things as unnatural, for example they believe that natural chemicals are different from laboratory chemicals.

Carolyn Schultz. There are some who won’t buy a synthetic food colouring or flavouring, even if they have the same chemical structure as the natural ones. We are unlikely to be able to convince these people that GMOs are beneficial.