Plant Science flourishes

Cologne's Max Planck Institute for Plant Breeding Research generates a new understanding of how plants work.

By Hildegard Kaulen

Scientist collecting samples from potato plants at the Max Planck's Institute for Plant Breeding Research greenhouse. © Maret Kalda, Max Planck Institute

Take any significant chunk of scientific history, and you'll find that an event from North Rhine-Westphalia is in there somewhere. For example, in June 1983, Jeff Schell of the Max Planck Institute (MPI) for Plant Breeding Research presented a method for gene transfer in plants. The vehicle that he and his colleagues used for gene transfer was a soil bacterium naturally equipped for the job: Agrobacterium tumefaciens. Schell's article on the subject in the EMBO Journal can claim to have ushered in the era of green biotechnology.

Since then, all four MPI Plant Breeding's departments have been among the front runners in plant research worldwide. The Institute has also had to face some pretty tough opposition from activists against genetically modified organisms. In the 1980s green biotechnology flourished more or less unhampered, but the gathering resistance against it in Europe in the 1990s finally culminated in a moratorium imposed across the whole of the European Union.

Even today, there is still a lot of opposition to gene transfer in plants from transnational advocacy groups. Heinz Saedler, another pioneer of green biotechnology in North Rhine-Westphalia, has witnessed demonization campaigns in all their variety. After years of altercations, Saedler concludes that those campaigns have successfully managed to play on people's fears, although there is not a shred of evidence that transgenic plants may be harmful. The only way tobreak down the resistance, he believes, is by laying out the facts, over and over again. Like the fact that today, 25 years after the first gene transfer and twelve years after commercial cultivation of transgenic plants started in the United States, genetically modified plants make up eight percent of the world's crops. The cumulative acreage planted since 1996 amounts to 1.7 billion acres, and in those 12 years over a billion people and many more animals have consumed bioengineered foods. There's no indication that it has done them any harm.

Arabidopsis thaliana seedlings grown on agar medium.

During the 1990s, the scientists at the Max Planck Institute for Plant Breeding Research began focusing on basic plant science using model species, but their findings continue to have enormous implications for agriculture. Among the topics under investigation are elucidating how plants know when to flower, how they defend themselves against pests, and what biodiversity really means.

Basic Instincts

The fact that scientists now recognize that plants have an immune system is the result of pioneering work by Paul Schulze-Lefert, a director of the Plant Breeding Institute for eight years. Initially, plants were believed to have inflexible and underdeveloped defense systems, but in a series of publications, Schulze-Lefert described the molecular foundations of sophisticated protection mechanisms. While they have neither circulation nor specialized immune cells, plants do have a dual radar system in each cell, one external and one internal. The external radar consists of a series of receptors. When one of these recognizes a pathogen, it sets off an alarm that triggers a defensive response. If the pathogen still manages to penetrate into the cell, it comes up against a second line of defense. If the relevant sensor is triggered the cell undergoes apoptosis, as a way of protecting the rest of the plant. "These two radar screens are a highly dynamic system based on resistance genes that constantly develop in the race against pests," says Schulze-Lefert. "The fact that whole crops are sometimes destroyed by pathogens has to do with the constraints placed on this co-evolutionary process ever since the pool of resistance genes started being restricted by breeding and vegetative reproduction. Our job is to give the plants new resistance genes, ideally combinations of them."

Among the topics under investigation are elucidating how plants know when to flower, how they defend themselves against pests, and what biodiversity really means.

George Coupland, another of the four directors, moved to MPI from the John Innes Center in Norwich, UK in 2001. His decision to relocate to Cologne was motivated by the excellent research opportunities provided by the Max Planck Society and the distinctive think-tank environment. Coupland investigates what tells plants when the right time has come to flower. "They take their bearings from day length and temperature," he says. "One of these processes is highly conserved, the other far less so. Plants measure day length in much the same way, whether they need a long or short day to trigger flowering. Temperature measurement seems to be something they have developed several times over in the course of evolution."

To activate an infestation, Maren Jagieniak from Bayer CropScience clamps pests onto cucumber plants.
Courtesy of Bayer crop Science

Two proteins play a special role in day length measurement. In the Arabidopsis plant, a complicated regulation system in the leaves ensures that one of these proteins is expressed only twelve hours after daybreak. If darkness has fallen by then, the protein will decay, but if daylight is still present, another gene will be expressed. Its gene product travels from the leaves to the apex, where it induces flower development. "We're working in very exciting territory," says Coupland. "First of all, we have finally identified the molecular details behind the control of flowering. Secondly, our findings benefit applied research. On the basis of our findings it will be possible to develop plant varieties whose flowering time is more precisely adapted to their location in high latitude or at high altitude."

High-yield variations

Maarten Koornneef from Wageningen, the Netherlands, is the current managing director at the Institute. He investigates natural variations in model and crop plants. Potentially, a variation that asserts itself in nature is an avenue for plant breeders to explore. Especially interesting are genes that help plants survive drought and frost or produce a higher yield with less fertilizer. "One of our central problems is resource limitation," says Koornneef. "Agricultural acreage is dwindling; the population of the world is increasing. That means we need high-yield crop plants that can flourish in unfavorable locations. Here, finding variations in nature, for example, in related wild species, can be very enlightening. New features can then either be introduced into the relevant crops by gene transfer or via plant crossing. Knowledge of where the genes are located and what the genes encode will make this introduction via classical breeding much easier, using DNA technology as a diagnostic tool."

"Producing tailor-made therapies from plants is especially interesting for personalized medicine."

Morphological novelty is also crucial to biodiversity, the field Heinz Saedler specializes in. To preserve biodiversity, we must know what a species is and how new species originate. "There are various levels of complexity to that problem," Saedler explains, "there is the diversity of genes, species, and ecosystems. Our main concern is with gene diversity and the question of how morphological novelties originate. Sometimes it appears as if all that changes is the context in which a gene is active." Saedler and his colleagues have demonstrated the point with reference to solanaceous plants. Instead of small calyx leaves, some Solanaceae form structures that envelop the fruit in a kind of balloon-like calyx. In this case, a protein required for vegetative development becomes active in a different context—in floral development.

Research in the Bayer CropScience formulation technique institute: To receive best possible efficacy, the optimal formulation has to be found.
Courtesy of Bayer crop Science

In North Rhine-Westphalia commercial interest in green biotechnology has always been keen. One of the first companies to stake its claim in this area was Bayer Crop Science with its business operation units Crop Protection, BioScience, and Environmental Science. The company explores the business potential of transgenic plants in its BioScience sector by using plant biotechnology and modern plant breeding techniques such as hybridization or molecular breeding to improve the quality of agricultural crops and vegetables. Together with Crop Protection, BioScience offers an integrated portfolio of high-quality seeds, trait technologies and high-performance crop protection products. The attendant BioScience Research center is located in Ghent, the town where Jeff Schell and Mark van Montagu laid the foundations for gene transfer in plants.

Climate change and dwindling crop acreage are forcing farmers to turn to areas that are suboptimal for agriculture. Accordingly, they need varieties with increased yield and high stress tolerance. It is by no means rare that 60-80 percent of crop yields are lost by abiotic stress factors such as drought, heat or too much salt in the soil. Bayer is working to develop more resistant varieties. The company also intends to produce pharmaceuticals from plants. In comparison to animal or bacterial expression systems, the advantage of plants is that they can be grown more cheaply and do not require optimization of the production process. It is generally a more robust expression system and plants do not host viruses that could be harmful to humans. Bayer has taken an important step by acquiring Icon Genetics, a company that has developed technology to express alien genes transiently. "This procedure is especially interesting for personalized medicine," says John Butler, project manager for "Plant-made pharmaceuticals" at Bayer Innovation GmbH, "tailor-made therapies require small amounts of biopharmaceuticals, a significant economic hurdle with traditional production schemes. In 2009 we are planning to test a plant-made vaccine in a phase-1 study in non-Hodgkin lymphoma. Every batch is tailor-made for a single patient."

It's been a long journey from Schell's groundbreaking work, but it's now clear that green biotechnology is here to stay.

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