Robert Pore's Ag Blog

Ghent, Belgium -- Using plants to produce useful proteins could be an inexpensive alternative to current medicine production methods. Researchers from the Flanders Interuniversity Institute for Biotechnology (VIB) at Ghent University have succeeded in producing in plant seeds proteins that have a very strong resemblance to antibodies. They have also demonstrated that these antibody variants are just as active as the whole antibodies that occur naturally in humans. By virtue of their particular action, antibodies are very useful for therapeutic and diagnostic applications. From this research, it is now also clear that these kinds of antibody variants can be used in medical applications and that it is possible to produce them in the seeds of plants, which can have enormous advantages over conventional production methods.

Production of biotech medicines

A large number of today's medicines are made with the aid of biotechnology (and this number should only grow in the future). To do this, scientists use genetically modified bacteria, yeasts, or animal cells that are able to produce human proteins. These proteins are then purified and administered as medicines. Examples of such proteins are antibodies, which can be used, for instance, in the treatment of cancer. The conventional methods for producing antibodies work well, but they are expensive and have a limited production capacity. The high costs are primarily due to the need for well-equipped production labs and to the labor-intensive upkeep of the animal cells, which are needed as production units.

Plants: a possible alternative?

For a number of years now, the VIB researchers in Ghent - Bart Van Droogenbroeck, Ann Depicker and Geert De Jaeger- have been searching for ways to have plants produce useful proteins efficiently. Plants do offer a lot of advantages over conventional production methods. Because production with plants doesn't require expensive high-tech laboratories, scientists anticipate that, by working with plants, production costs will be 10 to 100 times lower. Another important advantage is that large-scale production is possible without having to make additional investments in expensive fermentors.

A good yield guaranteed

Several years ago, Geert De Jaeger and his colleagues succeeded in achieving a high yield of an antibody variant in plants, which had been very difficult to do up to that time. The trick the researchers used was to modify the plants in such a way that they would produce the antibody variant in their seeds. With their special technique, the scientists succeeded in producing seeds in which the desired protein is good for more than one third of the total protein amount. This is a huge proportion compared to other systems - normally, scientists succeed in replacing only 1% of the plant's proteins by the desired protein.

Plant seeds are especially attractive as production units. In addition to a high production capacity, they offer other important advantages over other parts of the plant. The seeds can be stored for a long time without losing the produced protein's effectiveness, so that a reserve can always be kept on hand. This means that the proteins can be isolated from the seeds at the moment that they are actually needed. With production in leaves, for example - or with conventional production methods - such lengthy storage is not possible: the protein must be isolated immediately after production. So, production in plant seeds provides the clear advantage of timely processing.

High production of an efficient antibody variant

The antibody variant that has been produced by Geert De Jaeger and his team has a very simple structure and has only one binding place for a particular substance. Bart Van Droogenbroeck and his colleagues, under the direction of Ann Depicker, are now showing that it is also possible to produce more complex antibody variants in large quantities in the seeds of the Arabidopsis plant. Over 10% of the proteins in the seeds of these plants are the desired antibody variant. As is the case with whole antibodies, these more complex antibody variants have two binding places for a specified substance. This close similarity to whole antibodies makes these antibody variants extremely useful for therapeutic and diagnostic applications.

However, the production of proteins in plants is completed in a different way than in humans. Therefore, to be certain that this different completion process does not affect the effectiveness of the potential medicine; the scientists have subjected the action of the antibody variant to an exhaustive battery of tests. These laboratory tests have shown that the antibody variants produced in plants are just as effective as whole human antibodies in protecting animal cells against infection with the Hepatitis A virus.

This is a significant step forward in making protein production in plants a real alternative to current production methods.

Labels: Ag news: Science

EL BATAN, Mexico and ALEPPO, Syria — A new form of stem rust, a virulent wheat disease, has jumped from eastern Africa and is now infecting wheat in Yemen in the Arabian Peninsula.

Researchers with the Global Rust Initiative (GRI) and the Agricultural Research Service of the United States Department of Agriculture (USDA-ARS) have confirmed conclusively the existence of the disease in Yemen. There is also evidence that the disease has spread into Sudan but more tests are needed to confirm the finding. Until this discovery, this new strain of stem rust, known as Ug99, had only been seen in Uganda, Kenya and Ethiopia.

The last major epidemic of stem rust occurred in North America in the early 1950s, when a strain of stem rust destroyed as much as 40 percent of the continent's spring wheat crop. Out of this crisis came a new form of international cooperation among wheat scientists worldwide, spearheaded by Nobel laureate wheat scientist Norman Borlaug. This international alliance of scientists led to the development of wheat varieties which resisted the onslaught of stem rust for more than four decades. But in 1999, a new strain of stem rust was discovered in Uganda and Kenya capable of destroying most previously disease-resistant wheat varieties.

A year and a half ago geographic information systems specialists working at CIMMYT plotted the probable trajectory of the fungus, whose spores can travel large distances on the wind. The wind models predicted that if the fungus crossed from eastern Africa to the Arabian Peninsula it could easily spread to the vast wheat-growing areas of North Africa, the Middle East, Pakistan and India.

There is precedence for this, from a virulent strain of another wheat disease, called yellow rust, which emerged in eastern Africa in the late 1980s. Once it appeared in Yemen, it took just four years to reach wheat fields of South Asia. On its way, this new strain of yellow rust caused major wheat losses in Egypt, Syria, Turkey, Iran, Iraq, Afghanistan, and Pakistan, exceeding USD 1 billion in value. There is every reason to believe the new Ug99 strain of stem rust represents a much greater risk to world wheat production. Annual losses of as much as USD 3 billion in Africa, the Middle East and south Asia alone are possible.

According to the Food and Agriculture Organization of the United Nations (FAO), countries in the predicted, immediate pathway grow more than 65 million hectares of wheat, accounting for 25 percent of the global wheat harvest. "If we don't control this stem rust threat," says ME Tusneem, Chairman of Pakistan's Agriculture Research Council, "it will have a major impact on food security, especially since global wheat stocks are at a historic low."

Experiments conducted over the past two years by international researchers in the Global Rust Initiative in Kenya and Ethiopia demonstrate clearly that most of the world's wheat varieties are susceptible to the new Ug99 strain of stem rust. "This is a problem that goes far beyond wheat production in developing countries," warns Borlaug. "The rust pathogen needs no passport to cross national boundaries. Sooner or later Ug99 will be found throughout the world, including in North America, Europe, Australia and South America."

GRI scientists have already identified promising experimental wheat materials with resistance to Ug99. But from the first breeding trials to growing new, rust-resistant varieties in farmers' fields on millions of hectares takes time and a massive effort.

"If we fail to contain Ug99 it could bring calamity to tens of millions of farmers and hundreds of millions of consumers," says Nobel Laureate Borlaug. "We know what to do and how to do it. All we need are the financial resources, scientific cooperation and political will to contain this threat to world food security."

Labels: Ag news: Science