A forest in a petri dish

Molecular techniques are beginning to transform the forestry industry. Victoria's Department of Primary Industries' Forest Science Centre at Creswick has developed a way of growing wood in tissue culture, that enables researchers to rapidly determine effects of manipulating genes that influence wood growth and quality in long-lived forest trees.

Growing transgenic plantlets from tissue-cultured cells is routine practice in plant research laboratory cells around the world. But growing wood from large forest trees in a petri dish is an impressive feat, by any measure.

Dr Matthew Leach's technique opens a new world of possibilities in developing transgenic plantation forestry trees. Where it would normally take years to determine how gene surgery has changed the wood properties of long-lived trees like eucalypts, or radiata pine, Leach's system can deliver answers in three months -- not much longer than two life cycles for the plant geneticist's standard 'lab rat', weedy little Arabidopsis thaliana.

As an enabling technology, it's one of the most important pieces of intellectual property in international forestry, according to Dr Gerd Bossinger, head of the Creswick group.

Leach's technique involves taking small samples of rapidly-growing cambium tissue from trees, and growing them in culture. After the initial wound response, the tissue resumes normal growth, according to Bossinger.

"We can put in constructs that cause genes involved in wood growth to be over-expressed, or switch off genes using RNA interference," Bossinger says. The system allows researchers to track the development of heartwood from actively growing cambial tissue, and to tweak genes that influence production traits such as lignin and cellulose content, fibre length and microfibril structure.

The Creswick group's system is unique, says Bossinger, and the big multinational forestry companies that dominate gene discovery in forestry species, are taking a keen interest in its potential to explore gene expression, and changing gene-expression profiles as trees grow and mature.

Bossinger says his group is investigating the developmental processes that transform a tiny, dormant embryo in a seed into a mature tree. "When we find interesting things we can apply it towards specific outcomes. we plan to develop niche markets around plantation trees with specific wood-quality attributes."

In one project, the Creswick team is studying the processes that transform spongy, actively growing sapwood into dense heartwood -- timber.

"The process involves the translocation of polyphenolic compounds that give heartwood its darker colour," he says. "We now know that, just as in animals, it involves programmed cell death or apoptosis.

"But it's a much simpler system to study and manipulate, because it involves only one type of cell -- ray parenchyma cells."

Bossinger says the cells produce structures called tyloses that penetrate the tree's vascular system, sealing it off and making it impenetrable to microorganisms.

"The process is not very desirable, because it also makes the vessels impenetrable. The idea here is to induce ray-cell death before the cells become competent to form tyloses, so you would still have wood with all the desirable characteristics of heartwood, but it would still be penetrable for preservatives and stains.

"We already grow plantation forests for pulp and paper production, but the long-term goal is to develop trees that will produce old wood -- heartwood -- so that we can also use plantation trees to produce timber suitable for construction, or furniture, so we would no longer need to take it from our native forests.

"It's very basic science, but it's directly linked to applications. Wherever we touch these trees, there's a potential commercial outcome."

Export potential

The centre's director, Dr Mark Adams, says most big forestry companies around the world are looking at cloning elite trees, rather than growing them from seeds, for plantation forestry.

"The potential benefits of the technology are substantial -- they include reduced management, predictable growth, and reduced fertilisers," Adams says.

"We're developing a partnership with CSIRO Forestry and Forest Products. Some groups are using marker technology to identify elite trees, others are using more fundamental tools."

Apart from investigating the genetics of wood development and wood quality, the centre has PhD students investigating genes for salt tolerance. One has isolated a gene involved in sodium transport in Arabidopsis which, when over-expressed, confers high tolerance to salt. Adams says the immediate aim is not to develop salt-tolerant trees, but simply to understand how genes involved in salt tolerance are expressed to allow plants to cope with salty conditions.

Adams believes Australia can export its advanced forestry technology to the world's nations, as a valuable form of international aid.

"We should do more than sell them tractors, or give them new lines of wheat or rice," he says. "Maybe we can give them our tree lines, so that they can earn greenhouse credits while they develop their forestry industries.

"A lot of the biotech debates gets narrowed down to the purely commercial - but beyond commercial benefits, there are social and environmental benefits, and Australia can play a lead role."

Hexima hits a six

Meanwhile, a promising advance in crop protection technology from Dr Marilyn Anderson's research group at La Trobe University is now in the throes of commercial development.

Five years ago Anderson and Adrienne Clarke founded a small plant biotechnology company, Hexima, to commercialise Anderson's discovery of a gene that inhibits the ability of caterpillars to digest plant proteins.

Anderson's group has developed a transgenic cotton variety containing the gene, and is now seeking to conduct field trials.

The company's name refers to the six insecticidal domains of a gene, which came from ornamental tobacco. Each domain independently inhibits the proteinase enzymes that allow caterpillars to digest plant proteins.

Hexima's transgene is, in effect, six insecticidal genes in one, making it would be extremely unlikely that any insect pest could simultaneously evolve resistance to all six.

Anderson says the proteinase inhibitor would not be used as stand-alone protection for cotton or other crops; rather, it would reinforce the successful Bt delta-endotoxin technology deployed by agrobiochemical giant Monsanto, by building another layer of protection into crops like cotton.