Sharon Long's studies of signal transduction pathways in plants could yield insights into cancer and other diseases in humans.

At first, it sounds catastrophic. Some cells receive mysterious signals and begin dividing rapidly. They form one tumor, and then another. But these are not cells of the breast, or colon, or even of people. They are root cells of the alfalfa plant, and the tumors they form are root nodules that help fix nitrogen and promote growth.

If you wipe away the soil and peer inside these "good tumors," you may find biological secrets that help explain why cancer and other diseases occur in humans."A lot of signal transduction pathways are already known in mammals," said Sharon Long, an HHMI investigator at Stanford University. "But there may be thousands more. It may turn out that some of these can be identified first most easily in plants."

Long is alone among the Institute's 270 investigators in focusing primarily on plants rather than on humans, fruit flies, or other animals usually associated with biomedical research. Crossing boundaries is a familiar pursuit for Long. Her lab uses a variety of experimental approaches--from chemistry to cell biologyto learn about the interplay between alfalfa and bacteria. She is both researcher and teacher; employee and mother; scientist and church choir singer.

Long's recent discoveries about alfalfa and Rhizobium bacteria have caused many scientists to think more deeply about cell signaling. Each of the two organisms can grow in isolation. But placing them together leads to a pas de deux of gene expression and cell division. Long and her colleagues have identified and cloned genes in the bacterium that cause it to stimulate the alfalfa. The alfalfa responds by forming its root nodules, where the bacterium finds a cozy home. The nodule resembles tumorigenesis in animals, except that the growth is desirable. The triggering signal is a new category of compound that Long and colleagues are now studying in more detail.

"This experimental system provides a unique opportunity for studying cellular interactions and information control during development," said Long. Her research has won the attention of basic scientists, biotechnology firms and the agriculture industry. Her findings about nitrogen fixing in plants could lead to new kinds of fertilizers that enrich crops naturally, without harmful chemicals.

Long herself remains focused on the biochemical conversation between alfalfa and Rhizobium. "I like to get hold of a question and let it lead me," she said. Judging from the past, Long will lead a lot of people along with her.