Life Lines 12

A ROSE IS A ROSE IS A PRODUCT OF FIVE GENES NECESSARY FOR FLOWER DEVELOPMENT

Few things irritate those in the humanities more than the efforts of science to reduce the metaphorical, complex, and beloved through the reductionism of experimental analysis. The image of scientists plucking sepals, petals, stamens, carpels, and ovules from a flower is debasing to the aesthetic sense of a rose. One thinks of Charles Dickens’ horror in Hard Times, when a student defines a horse as a “gramniferous quadruped” to the teacher’s (appropriately named Gradgrind) delighted but sterile soul. But such studies lead to medical cures, commercial applications in horticulture, new varieties to delight the eye, new scents to bring ecstatic responses, and many an amorous kiss when flowers are delivered from one lover to another. For scientists it is the understanding that trumps all of these otherwise desirable uses of new knowledge. Why new knowledge is so threatening is difficult to understand because every scientist I know who has made a discovery will describe the thrill as akin to writing a novel, composing a poem, working out a dance routine, composing music, or painting a landscape. Think of the pleasure it must be to wrestle one more unknown from nature.

In the 1970s two laboratories independently isolated three (now there are five) genes associated with floral development. They gave them the generic letters A, B, and C (now D and E have been added) and they called their theory the ABC theory of floral development. That’s easier to remember than to call it the Coen-Meyerowitz theory. If you look at a flower and (shudder) strip it of its components, the outermost will be the sepals, which are usually leaf-like. Then come the gorgeous colored petals. Next come the male organs or stamens; then innermost is the female organ or carpel with its inner treasure, the ovules. All have gene E. Sepals add an A. Petals have A and B as well as the E. Stamens dump the A and replace its function by turning on gene C. The carpel turns off the B and that leaves C and E. The ovules add the D function and that makes them CDE. Scientists can mutate any of these five genes and make abnormal flowers lacking one or more of these structures or putting the wrong component in the ring of structures we call a flower. It’s possible to convert hermaphroditic plants into two sex plants, one bearing stamens and the other bearing the carpels.

Molecular botany is having a great time identifying genes for flower scent formation, flower color, and making plants to order for different climates. The horticulture business generates 50 billion dollars a year so they are quite happy to hire molecular biologists to develop new varieties. They are also identifying and synthesizing the thousands of plant scents and floral pigments. There are genes for petal number, petal shape, and petal texture. For many of these botanists, it is like selecting fabrics to make quilts or dresses. It is like an artist’s palate of colors squeezed from tubes. We love seeing the gorgeous carmine used to paint a rose, but we would be aghast when told that is produced by scraping off thousands of scale insects from a cactus and crushing them to a powder to make the carmine dye. Sometimes we prefer not be in the kitchen to see how gourmet food is made. We prefer the mouth-watering fantasy of a gorgeous cut of T-bone steak and not the sight of a gutted carcass from which it comes.