Moby-Dick, the gigantic sperm whale sought by Captain Ahab in Herman Melville's 1851 novel, was merely one of its kind under human assault. From relentless hunting across two centuries, numbers of this endangered species (Physeter catodon) plummeted from many millions in the world's oceans to fewer than 10,000 individuals today. In the 1980s, the International Whaling Commission (IWC) finally imposed an indefinite moratorium on the commercial hunting of many declining cetacean species, sperm whales included, but some harvesting nations, notably Japan and Norway, still fail to comply forthrightly with all of IWC's stipulations.
The sperm whale is among the largest mammals in the world, capable of reaching 80 feet or more in length, with a weight of 40 tons. However, it was not so much the blubber surrounding the leviathan's body that whalers sought, but rather a fine waxy oil filling a cavernous organ, the spermaceti, inside the whale's prodigious head. The spermaceti, from which the species name derives, holds up to 500 gallons of the precious cream that whalers sold for use as lamp oil, candle wax, watch lubricants, and, more recently, additives for motor oils and transmission fluids, rust-proofing agents, detergents, lubricants for delicate high-altitude instruments, cosmetic bases, and more than 70 pharmaceutical compounds. Beginning in the mid-i800s, kerosene and other petroleum products steadily replaced sperm oil as affordable illuminants and greases, but other uses kept demand high for this exceptional whale substance.
Some 30 years ago, university researchers discovered an amazing analogue of sperm-whale oil in the inch-long seedpods of a desert plant, the evergreen shrub jojoba (Simmondsia chinensis). Native to the Sonoran region of the American Southwest (the Latin species name is a misnomer), jojoba produces a fine wax that Indians used for hair care and other purposes, but that now finds manufacturing applications ranging from shampoos and hair conditioners to pharmaceuticals and automotive lubricants. Commercial harvesting of wild jojoba seeds began in the early 1970s, and agricultural plantations quickly were established in semiarid habitats in the United States, Israel, and elsewhere. Jojoba oil is light yellow, highly pure (requiring little refining), and stable to temperatures of 300oC or higher without losing viscosity. In short, it is a fine substitute for whale oil in many applications, and for this reason it alleviated hunting pressures on beleaguered sperm whales.
However, the limited availability of jojoba oil keeps its price quite high relative to petroleum-based products. Accordingly, geneticists are seeking ways to engineer more traditional crop species so that they, too, can produce jojoba oil. Toward that end, experimental mustard plants (Arabidopsis) have once again been employed.
The jojoba shrub is unusual among plants in using waxes (rather than triacylglycerol fats) as the storage lipids in its seeds. Wax synthesis occurs in the plant embryos where enzymatic activities convert oleic acid molecules into the very long chain, mono-unsaturated fatty acids and fatty alcohols that make up its waxy substance. Three key enzymes in the process are wax synthase, fatty acyl-CoA reductase, and b-ketoacyl-CoA synthase. DNA sequences for genes specifying these enzymes were identified from jojoba (and Lunaria annua, another plant that accumulates long-chain fatty acids in its seeds), cloned into plasmid vectors of Agrobacterium tumefaciens (see "Galls and Goals" in the appendix), and inserted into the Arabidopsis genome. The enzymes were expressed in these transgenic plants and produced waxy substances that constituted up to 70% by weight of the mustard seeds. The next step will involve attempts to engineer wax-making capabilities into more traditional crop species, such as cauliflower or turnip (related to Arabidopsis), for commercial harvests.
Various other crop plants naturally produce diverse fatty acids, oils, and waxes that genetic engineers are aiming to improve for consumer health benefits or other commercial applications. The castor plant (Ricinus communis), from which castor oil derives, illustrates both goals. Approximately 90% of castor oil is ricinoleic acid, a useful compound in lubricants, paints, cosmetics, and as a cathartic (bowel purgative), but the seed coat of the bean itself is rich in ricin, an allergenic and potentially fatal protein. Using genetic engineering technologies, scientists are trying to alter the ricin to a less harmful form. They are also trying to modify the plants to produce, instead of ricino-leic acid, a closely related epoxy oil that would be useful in the manufacture of premium oil-based paints.
Because agriculture is involved, this essay could just as well have been placed in chapter 4. I include it here, however, to highlight an environmental issue: the notion that some GM crops producing commercial compounds might on occasion help save wild populations of endangered species. The oils and waxes from GM plants described above, especially had they been available in earlier times, in principle might have helped alleviate hunting and harvesting pressures, respectively, on sperm whales and jojoba plants, species from which those valuable substances otherwise have been derived. Such possibilities, as well as the potential commercial value of such compounds, provide my rationale for a rating of hope in the boonmeter.
BD HY HO BO
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