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around to seed development, that would be the end of the project. blocked by a piece of DNA in between the promoter and the cod- There would soon be no viable seeds to sell to farmers. ing sequence. The Terminator patent offers an ingenious method for keeping 2. A repressor protein coding sequence with a promoter that is the toxin gene from being active until long after the farmers plant active all of the time. their crops. The trick is accomplished by inserting a piece of 3. A recombinase coding sequence, controlled by a promoter DNA in between the seed-specific promoter and the toxin coding that would be active at all times, except that it is also regulated by sequence that blocks it from being used to make protein. repressor protein which can be overridden with tetracycline. At either end of the blocking DNA are put special DNA pieces The actual transfer of genes into the plant is not a very precise that can be recognised by a particular enzyme, such as the enzyme operation. Any one of a variety of methods can be used: the called ‘recombinase’. Whenever the recombinase encounters these genetically engineered DNA can be injected into the nucleus of a DNA pieces, the DNA is cut precisely at the outside of each cotton cell with a tiny needle; or plant cells can be soaked in the piece, and the cut ends of the DNA fuse together, with the result DNA and electrically shocked; or the DNA can be attached to that the blocking DNA is removed. When this happens, the seed- small metal particles and shot into the cells with a gun; or viruses specific promoter is right next to the toxin coding sequence and is and bacteria can be engineered to infect cells with the DNA. able to function in making the toxin. But this does not happen In all cases, the genetically engineered DNA has to find its way immediately. Toxin will not be produced until the end of the next to the nucleus and become incorporated into the plant chromo- round of seed development, because that is when the LEA pro- somes. The number of copies of the inserted genes and their loca- moter is active. Thus, after the recombinase enzyme does its tions on the plant chromosomes are unpredictable, and how well work, the plant grows normally from germination, through growth the new genes will function hangs in the balance. of stems, leaves and roots, all the way through flower formation, It takes a lot of effort to locate cells that have incorporated pollination and most of seed development. Then, on cue, the DNA in significant amounts and in locations that work. seeds die. Basically, whole plants have to be regenerated from the cells or All this accomplished, there remains one more problem: how tissues that were transformed with the foreign DNA, and then to grow several generations of the genetically engineered variety each plant has to be tested for the presence and function of the so that its seed can be multiplied to new genes. sell to farmers. After plants with well-functioning The Terminator patent solves the new genes are identified, they are dilemma by preventing recombinase then mated in combinations that from acting until just before the farm- It is likely that Terminator will result in a line of cotton where both ers plant their seeds. The patent-hold- sets of chromosomes, in all of the ers give several possible ways to do kill the seeds of neighbouring offs ring, have all the components hs conenateon he ollvine | plants of the same species J test or Teminaure tnson They propose putting a recombi- under certain conditions. make a large quantity of seed for sale. In effect, Terminator Technology gives the seed producer the ability to determine when to set Terminator in motion. Until the recombinase is nase coding sequence next to a pro- moter that is always active in all cells, at all times, but is repressed. The pro- moter can be made active again (de- repressed) by a chemical treatment. Therefore, the seed sellers can treat the seeds right before planti- made, the cotton plants grow normally. After recombinase is ng, thus allowing the recombinase to be made then, but not made, the second generation of seeds is killed, thus protecting the before. patented variety. One of the repressible promoter systems they discuss in detail is controlled by the antibiotic, tetracycline. A gene that makes a Some Problems with Use of Terminator Technology repressor protein all of the time would be put into the cotton plant, The patent on this technology is complex. I have described along with a recombinase gene that has a promoter engineered to only one of many possible applications of the procedure. Clearly, be inactivated by the repressor protein. Under most conditions, one cannot determine ahead of time all the possible biological then: the repressor would interact with the recombinase gene; no ramifications of implementing the patent. However, potential recombinase would be made; the toxin gene would be blocked; problems have already been noted (Ho, 1998). I deal with some and no toxin would be made, even during seed development when of them below. the LEA promoter normally would be active. To activate the toxin gene, seeds just starting to germinate - Will the Terminator spread to other plants? would be treated with tetracycline just before they are sold to It is likely that Terminator will kill the seeds of neighbouring farmers. The tetracycline would interact with the repressor pro- plants of the same species under certain conditions. However, the tein, keeping it from interfering with production of recombinase. effects will be confined to the first generation and will not be able Recombinase would be made, cutting out the blocking DNA from to spread to other generations. the toxin gene. The toxin gene would now be capable of making The scenario might go like this... When farmers plant the toxin, but would not actually do so until the end of seed develop- Terminator seeds, the seeds already will have been treated with ment. The next generation would thus be killed. tetracycline, and thus the recombinase will have acted and the To accomplish the Terminator effect in cotton, then, three engi- toxin coding sequence will be next to the seed-specific promoter neered components must all be transferred into a cotton plant's and will be ready to act when the end of seed development comes DNA. around. The seeds will grow into plants which will make pollen. 1. A toxin gene controlled by a seed-specific promoter, but Every pollen grain will carry a ready-to-act toxin gene. If the plants of the same species | under certain conditions. Some Problems with Use of Terminator Technology The patent on this technology is complex. I have described only one of many possible applications of the procedure. Clearly, one cannot determine ahead of time all the possible biological ramifications of implementing the patent. However, potential problems have already been noted (Ho, 1998). I deal with some of them below. - Will the Terminator spread to other plants? It is likely that Terminator will kill the seeds of neighbouring plants of the same species under certain conditions. However, the effects will be confined to the first generation and will not be able to spread to other generations. The scenario might go like this... When farmers plant the Terminator seeds, the seeds already will have been treated with tetracycline, and thus the recombinase will have acted and the toxin coding sequence will be next to the seed-specific promoter and will be ready to act when the end of seed development comes around. The seeds will grow into plants which will make pollen. Every pollen grain will carry a ready-to-act toxin gene. If the 28 - NEXUS It is likely that Terminator will kill the seeds of neighbouring DECEMBER 1998 - JANUARY 1999