Wheat grain with more protein
(02 Aug. 06/01 Dec. 06) A release trial with genetically modified winter wheat began on Monday in Saxony-Anhalt. The trial, submitted by the Leibnitz Institute of Plant Genetics and Crop Plant Research (IPK) in Gatersleben had previously been approved by the Federal Office of Consumer Protection and Food Safety (BVL) under certain conditions. Two genes from barley and broad beans have been inserted into the wheat. The aim is to increase the protein content in the wheat grain.
In the 2006/2007 and 2007/2008 growing periods, around 11 200 plants will be planted out on an area measuring around 1200 square metres.
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A number of GM wheat lines are being tested in the release trial. The transferred genes come from barley and broad beans and code for special proteins that are responsible for transporting sugars and amino acids to the developing corn. Under greenhouse conditions it was observed that the activity of these genes leads to higher protein levels in the seeds of the wheat lines.
Proteins are some of the most important basic nutrients and are essential for growth and development. Important sources of protein are animal products like meat, fish, milk and eggs, and plant seeds. Seeds that are particularly rich in protein are pulses like soya, peas, lupins and broad beans (25-50 per cent protein). Cereal grains have a much lower protein content (9-12 per cent). Although cereals are largely used as a source of starch, plant-breeders have been attempting to increase the protein content for a long time – so far without success. Despite decades of attempts, it has not been possible to achieve this aim using conventional breeding techniques without incurring significant yield losses. |
More transport proteins, more proteins in the wheat grain
Genetic engineering has opened up new possibilities. The starting points are the biochemical processes that lead to the production of proteins in seeds. The vegetative phase, in which the plant produces foliage, is followed by flower and seed formation (the reproductive phase). The building blocks of the proteins, the amino acids , are transported from the vegetative parts of the plant, e.g. the leaves, via pathways in the stem and shoots to the young, developing seeds. A similar process occurs with the sugar building blocks, which are needed to build starch and as carbon structures for the amino acids. In the seeds, the amino acids are joined together to produce the seed storage proteins typical of the plant group.
Amino acids and other raw materials needed for building proteins in the seeds are transported with the help of certain transport proteins. Several of these transport proteins and the associated genes have been isolated, characterised and investigated at IPK Gatersleben over recent years. The obvious question was: is it possible to achieve increased amino acid transfer to the seeds, and thereby increase the protein content through the increased production of certain transport proteins?
In an earlier experiment, this conjecture was indeed confirmed: the scientists first transferred a gene for a certain transport protein (VfAAP1, Vicia faba amino acid permease 1) isolated from broad beans into a related species of bean and into peas. The total nitrogen content – an indicator of protein formation – rose significantly in both plants.
In parallel experiments, researchers inserted the VfAAP1 gene into Certo, a variety of winter wheat. In addition, wheat lines were produced that contain a gene from barley (HvSUT1), which codes for a saccharose transporter. The expectation was that this might lead to greater numbers of carbon structures and consequently to increased protein synthesis.
Initial investigations with greenhouse plants showed that the expression of the VfAAP1 gene and the expression of the HvSUT1 gene both lead to increased protein content in the wheat grain. However, only field trials can provide assurance that such a strategy will work under realistic farming conditions.
There are no plans to develop the transgenic wheat lines into new commercial varieties. The purpose of the trials is to test the new approach to increasing the protein content under field conditions. This is why the marker genes used to produce the wheat lines have not yet been eliminated. The GM wheat lines contain a plant selection marker (resistance to the active herbicide ingredient glufosinate ) and two bacterial antibiotic‑resistance markers .
IPK: Release trial poses no threat to the gene bank
In its approval, the BVL states that the planned trial will have no harmful impacts on human or animal health or the environment. It states that the probability of outcrossing is to be regarded as generally low. As a self-pollinator, the wheat fertilises itself inside the flower with its own pollen. As a precaution, however, a minimum distance of 120 metres must be respected from other wheat fields, and 500 metres from the IPK gene bank propagation fields. The release area is also shielded from the gene bank field by a buffer planting as well as bushes and trees. In addition, the BVL has ordered other precautionary measures. The trial field must be fenced off, so that wheat grains cannot be carried off by wild animals, and the field must be covered by a bird net when the wheat ripens.
The BVL received 30 000 objections to the trial in Gatersleben. In particular, its critics feared that the trial could lead to incrossings of GM wheat into the rare plants on the propagation fields belonging to the gene bank and that valuable genetic resources could be endangered. A small proportion of the seed samples stored in the gene bank are planted out each year and propagated in the field.
The IPK countered these objections, stating that avoiding outcrossings between plants of different origins had always been "the highest priority of the gene bank’s work." Molecular tests had shown that the current cultivation practice for wheat has been successful in this regard. According to the IPK, for over fifty years thousands of different wheat strains have been propagated several times in the field without leading to any identifiable hybridisation.
With a total stock of around 150,000 specimens from 2,500 species, the IPK’s gene bank is one of the largest establishments of its kind in the world. It plays an important role in preventing crop plants and their wild relatives from dying out.
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