Wednesday, June 27, 2007

You say tomasil, I say bamatoe ...

There are some food combinations which reoccur frequently in the culinary arts. The pairing of basil and tomato is not only a dominant part of many Italian dishes, but is a great way to add zing to a BLT (or, if your vegetarian or keep kosher, to have a B for BL). Conventionally this is done by separately growing basil and tomato plants, harvesting the leaves and fruits respectively, and co
mbining them in the kitchen.

An Israeli group has published a shortcut to the process at Nature Biotechnology's advance publication site. By transferring a single enzyme from lemon basil to tomato, the authors report significantly altering the aroma and flavor of the transgenic tomatoes.

If you aren't a gardener, you probably haven't run into lemon basil. There are a whole host of basil varieties with different aromas and flavors, with some strongly suggesting other spices such as cinnamon. Basil is a member of the mint family, many of which show interesting scents. Look down your spice rack: many of the spices which are not from the tropics are mints: oregano, thyme, marjoram, savory, sage, wild bergamot, etc. Many of these come in multiple scents: in addition to peppermint and spearmint, there is lemon mint. Thymes come in a variety of scents, including lemon. If you have an herb garden, gently check the stems of your plants -- if they are square, it is probably a member of the mint family.

Of particular interest is the pleiotrophic ffects of the transgene. The inserted gene, geraniol synthase under the control of a ripening-specific promoter, catalyzes the formation of geraniol, an aromatic alcohol original extracted from geraniums. Geraniol itslef apparetnly has a rose-like aroma, but a number of other compounds derivable from geraniol were also increased, such as various aldehydes and esters with other aromas such as lemon-like. This reflects the fact that tomatoes possess many enzymes capable of acting on geraniol. Conversely, the geraniol was synthesized from precursors that feed into the synthesis of the red pigment lycopene and a related compound phytoene, and both of these compounds were markedly lower in the transgenic plants. The tomatoes appear to still be quite red, and well within the wide range of crimsonosity found in tomato varieties. This should come as no surprise to many gardeners: catalogs always warn that trying to grow spearmint or peppermint from seed is not guaranteed to get the right scent. Presumably there are many polymorphisms in monoterpene processing enzymes in the mint genome, and depending on which you assort together you get a different potion of fragrant compounds.

Volunteers sniff-tested and taste-tested (well, got some squirted in the back of their nose -- 'retro-nasal'). Testers generally preferred the smell and 'taste' of the transgenics. Most marketed transgenic plants affect properties key to growers but not consumers; you can't really tell if you have transgenic corn flakes or soy milk without PCR or an immunoassay (or similar). But with this transgenic plant, the nose knows.

Of course, the next line in the alluded-to song is "Let's call the whole thing off". There are many who oppose this sort of tinkering with agricultural plants for a variety of reasons. Myself, I'd leap at a chance to try one. I love tomatoes, provided they are fresh from the garden, and having one more variety to try would be fun!

Note: you need a Nature Biotechnology subscription to access the article. However, Nature is pretty liberal about giving out complimentary subscriptions (I once accidently acquired two), so keep your eye out for an offer.

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