Stanford scientist studies the sex life of corn

From Silicon Valley's Mercury News.com: Stanford scientist studies the sex life of corn

In a sun-dappled cornfield on the Stanford University campus, romance is in the air.

There's a LeBron James-like swagger to the tall male tassels. Round female ears await, coquettishly.

But corn conception, and development, is poorly understood. So biology professor Virginia Walbot devotes her career to tackling one of botany's big puzzles: the sex life of corn.

"It is really one of the deep, fundamental mysteries of plants," she said during a recent walk through late summer's towering stalks. "It is exceedingly important to understand every step of the process, so we can produce better seeds for American farmers."

Her lab's discoveries in developmental biology could help change how corn is grown and boost yield.

An estimated 80 million acres of corn are planted in the United States every year. Innovations in plant reproduction could add to the productivity of that acreage if, for example, farmers could plant more densely and use less gas, fertilizer and water.

But that juicy ear on your picnic plate? It almost didn't happen.

The parent plant could have just as easily decided to make a big green leaf instead, Walbot said. No one knows why, or how, corn decides to create a female ear or a male tassel. Or simply grow more vegetation.

"How does that switch occur, from being vegetative to reproductive? What are the early steps that it commits to, to produce sperm or eggs?" she said. "It's still unclear."

Walbot has a lifelong affection for corn, having helped grow and sell it from her family's truck farm in Southern California, on fertile acreage now covered by a runway at Los Angeles International Airport.

As a little girl, "I asked for plants, not dolls," she recalled.

Studying at Stanford, then Yale University, she became interested in the bigger picture: plant development and evolution. The most pivotal moment in her life came in the 1970s, when she met pioneering geneticist Barbara McClintock, who also worked with corn. They shared long phone conversations, then Walbot visited McClintock's Cold Spring Harbor lab -- and she was hooked.

Rich corn history
Like McClintock, Walbot is part of a long tradition of scientists who have found corn to be the perfect organism for answering some of the fundamental questions about plant genetics and development.

That's because each ear has a few hundred seeds, making it easy to generate huge populations very quickly. This means that even a rare event, like a particular mutation, is easy to find.

Her small Stanford field is rich with corn history, evoking memories of "The Farm" that drew founder Leland Stanford to the peninsula. Adjacent is the small summer home -- now boarded up, its paint peeling and doors latched -- where Nobel Prize-winning geneticist George Beadle lived in the early 1940s so he could be close to his plants.

"We keep track of every ear, in perpetuity," she said. "It's like the kings and queens of England. We can go back 30 years and tell you the whole history of a plant -- who's who. ... It's very valuable material."

There's nothing illicit going on in this field. Rather, Walbot's team practices "safe sex," so each pollination is carefully controlled. Walbot pollinates by hand, carefully selecting mates.

Then, to prevent added random pollination, the pollen-laden tassels are covered with paper bags so they won't drift onto nearby ears, which are the corn's eggs. The ears are also bagged. Then each bag is identified with the date of pollination, and its parentage: "8/16 - 88-11," for instance.

In these dwindling summer days, pollination is almost over. Then Walbot will wait for seed to mature.

She'll harvest from Sept. 20 to Oct. 10. Then the ears will be placed on wax paper and stored for a week in a warm walk-in drying room.

Once dried, seeds are stored -- they can last a decade -- in a special room near her campus laboratory, where it's cool and dry. Or they may be sent to a national seed bank in Illinois; Stanford has contributed 40,000 seeds there.

Answers in the shoots
Using microscopes and high-end tech tools, Walbot studies the kernel's DNA to learn what genes, or sequence of genes, might trigger development. She also studies mutations that alter how genes behave.

This is what's different about plants: Unlike animals, they are continuously making new organs, like leaves, from scratch. So scientists such as Walbot can study the development of the same type of organ, over and over.

"It's like a human producing new hands every week," she said. "If you need to repair a watch, you'd grow little bitty hands. Or if you want to play the piano, you'd grow really long fingers.

"We don't have that flexibility, but a plant does."

She thinks this difference relates to how creatures respond to stress. Animals can move when times get tough. But plants are stuck in place -- so they're forced to change. They might drop leaves. Or if times improve, add new leaves, grow tall, or reproduce.

But how? In the tips of their shoots is a complicated sequence of genetic on-off switches. That's what she seeks to better understand.

"If we understood this early step, we could inhibit it," she said, so farmers could hit a pause button on reproduction. "Or we could help engineer a tassel that's not so huge ... so the plant's energy goes into making more and larger kernels."

So she waits for her new kernels to mature in late summer's warm sun, hoping that nature will reveal, begrudgingly, a new clue to the genetic puzzle of plant development.

"Every question that is answered raises three more questions," she said, brightly. "You always have more things you can explore, rather than fewer, over time."