Sucrose synthase and the fruit of its labor.

Evolutionary selective pressures have clearly induced animals and plants alike to place a premium on liberal locomotive abilities. Because the root systems of plants define a sedentary existence, however, angiosperms in particular invest significant energies in exploiting the mobility of animals. Such exploitation, in fact, is one of the most fascinating evolutionary trends to have marked the biology of angiosperm reproduction. The enormous expenditure of genetic resources for the elaboration of distinctive floral chromophores that appeal to insects, or of scents that can attract the blindest of bats, is waged solely to recruit pollen-dispersing vectors. Seed dispersal is a second aspect of plant reproduction that is often facilitated by animal motility. Organs such as burrs—which, botanically speaking, are seed-bearing fruits—are shed so as to adhere to the fur, feathers, and skin of mobile animals. Similarly, the deployment of carbohydrate into edible fruits, thereby endowing them with their characteristic sweet and sour tastes, can function to entice foraging animals, often with the result that ingested seeds are distributed quite considerable distances. The fact that the average American consumes between 250 and 300 pounds of fruit annually bespeaks the success of angiosperms, albeit with the occasional intervention of horticulturists, in appealing to the human palate. The contingencies that lead to savory fruits, of course, are not only of agronomic and gastronomic interest. Indeed, fruit development and growth encompass a variety of questions that are basic to plant biology, many of which are only now beginning to be addressed at the molecular level. The investment of plant resources into fruit production makes evolutionary reproSucrose Synthase and the Fruit of Its Labor