Stearic acid 18 : 0 is a major component of cocoa butter,while oleic acid 18 : 1, n-9 is the major constituent of olive andoilseed rape oil. Promoters of this type are not active until theyare induced by something such as attack by a pathogen, grazing orapplication of a chemical. Theexact economic impact is difficult to gauge. Les informations fournies dans la section « A propos du livre » peuvent faire référence à une autre édition de ce titre. For example, the laboratorymust be easy to clean, bench-tops and floor must be sealed and ifthe laboratory is mechanically ventilated the air flow must beinwards. Nevertheless, Bt potato may have a role to play in Eastern Europeand Russia where the Colorado beetle is a huge problem. Contrary to the popular notion that natural is good andman-made is bad when it comes to food, plants did not evolve tobe eaten.
For plant scientists in the United Kingdom and the rest ofEurope the situation remains a frustrating one. Many plants producelectins as natural insecticides but most lectins are unsuitable for usein plant biotechnology because they are poisonous to animals,including humans. Another application being pursued by Johnathan Napiersteam and by several biotech companies is the production ofmarine fish oils in plants. The dwarfinggenes concerned actually affected the synthesis of a plant hormone,gibberellin, although that was not known at the time. There has been some success in recent years in usingmutagenesis to produce non-toxic forms of some adjuvants andexpressing these in plants, but the technology still requires somedevelopment and safety testing. Ultimately its productsare maltotriose, maltose and limit dextrin a mixture of branchedand unbranched glucans and the process is known as gelatinisa-tion and liquefaction. This was seen as the start of a biotechnological revolution in plant breeding.
Sanger andGilbert shared the Nobel Prize for Chemistry with Berg in 1980. Hormones produced by the shoot itself then induce rootformation and a complete plantlet is formed Figure 2. The starch fromthis new potato variety is composed almost entirely of amylopectin,whereas normal potato starch contains approximately 20% amy-lose. Most of these patents have never been tested incourt and it is still unclear to what extent they will be effective. The other side of the coin is that genetic modification could be usedto remove allergens from the food chain. Once shoot and root are fully formed,the plantlet can be transferred to soil and treated like any otherplant Figure 2.
It has been achieved in plants using gene constructs in which partof the gene is spliced sequentially in a head-to-tail formationdownstream of a single promoter. Together they arenatures genetic engineers and were using plant genetic modifica-tion millions of years before humans invented it. Gluco-amylases are then added to producesmaller sugars that can be fermented; this process is known assaccharification. The result is an accumulation of the 12-carbon chain lauric acid toapproximately 40% of the total oil content, compared with 0. As described in the previous section, the UidA codingsequence encodes an enzyme called -glucuronidase that producesa blue pigment from a colourless substrate. It had a cluster of tenderyoung leaves at the top of the plant and is known today as cabbage.
Other vaccines of this sort produced in plants includea rabies virus antigen in tomato, a cholera antigen in tobacco andpotato, the Norwalk virus capsid protein in tobacco and potato,and a human cytomegalovirus antigen in tobacco. Calgene wassubsequently acquired by Monsanto, who have so far not pursuedthe technology further. Plant molecular biology came to the fore in the early 1980s and there has been tremendous growth in the subject since then. Nevertheless, the industry and regulators are clear that every pre-caution should be taken to ensure that no new allergens areintroduced into the food chain through genetic modification. Thosethat are best fitted for their environment are the most likely tosurvive, reproduce and pass on their characteristics to the nextgeneration. This gene encodes a nitrilase enzyme that detoxifies the herbicide Figure 3.
More confusion is generated by the fact that different countrieshave different patenting laws and interpretations. They have therefore looked further afield, to exotic varietiesand wild relatives of crop species, for genes to confer importantcharacters. Gene over-expression and silencing -- 3. Picturekindly provided by Pilar Barcelo. The fact is that very few foods consumed today have beensubject to any toxicological studies, yet they are generallyaccepted as being safe to eat.
Techniques for plant transformation by Agrobacterium tumefaciens and particle bombardment, and for the selection fo transgenic plants using marker genes are described. The most successful of these is floral dip transforma-tion. . Indeed, improved yield was never a tar-get for herbicide-tolerant crops in a developed country wherefarmers have access to a variety of weed control measures. The technology has also been applied to viruses that affect live-stock.
Erucic acid see Chapter 3 is a fatty acid that hasbeen linked with the formation of fatty deposits in heart muscleand consequent muscle damage. In the second edition, sections on current Gm crops and future developments in plant biotechnology have been greatly expanded, while those on techniques, legislation and the Gm crop debate have also been updated. As described above,high temperature causes wheat and other cereals to develop andmature more quickly; it also brings about an increase in respirationand an inhibition of photosynthesis. There are no wild hexaploid wheat species:bread-making wheat appeared within cultivation in south-westAsia approximately 10,000 years ago and its use spread westwardsinto Europe. This was seen as the start of a biotechnological revolution in plant breeding. However, plant biotechnology has become one of the hottest debates of the age and, in Europe at least, one of the greatest challenges that plant scientists have ever faced. Ingo Potrykus, a biotechnologist at the Swiss Federal Instituteof Technology in Zurich, saw the possibility of using a comple-mentary approach through the genetic modification of rice, thestaple crop for many subsistence farmers.