Developmental Biology, Plant Biology
California Institute of Technology
Dr. Meyerowitz is a Howard Hughes Medical Institute–Gordon and Betty Moore Foundation investigator. He is also George W. Beadle Professor of Biology at the California Institute of Technology.
Genetic, Genomic, and Computational Studies of Plant Stem Cells
“The less I see my name in lights, the better,” says Elliot M. Meyerowitz. But he may have to get used to it. According to colleagues, the Caltech scientist is one of the world’s most productive and influential plant biologists.
Meyerowitz helped solve a problem that puzzled biologists for more than a century—how plants create their characteristic patterns of leaves and flowers. He and his team were the first to find a receptor for any plant hormone. He also led the effort to adopt Arabidopsis, a small flowering plant related to mustard and cabbage, as a model organism, and spearheaded a push to have the plant’s entire genome sequenced. And he’s been a tireless crusader for openness and collaboration in science, twisting arms behind the scenes to make plant DNA and other basic resources available to everyone.
Not bad for a man who describes himself as “basically an ordinary guy who likes doing science,” and who wasn’t even sure if he’d major in biology as an undergraduate at Columbia University. The key moment came when Meyerowitz needed to find a job to pay for college. He asked professors if they needed help in their labs and found himself working half time each year (and full time for two summers) with molecular biologist Cyrus Levinthal, known for his work on RNA metabolism and protein structure. “That’s what really set me on the course of science,” Meyerowitz says.
He finished his Columbia degree at the height of the Vietnam War, so graduate school at Yale beckoned. He started off probing the genetics of the fruit fly, Drosophila melanogaster, but soon heard the siren song of the plant kingdom. “I thought it would be good fun to do developmental genetics in plants,” he says. So he became the only animal scientist to drop in on Yale’s grad student seminars in plant research.
Once Meyerowitz had his own lab at Caltech, he could finally indulge his interest in plants along with Drosophila. He began to study Arabidopsis and showed that the plants had a very small genome with few repetitive DNA sequences. It was the first hint that Arabidopsis would be a perfect candidate to become a model organism. As his work with plants flourished, Meyerowitz became fascinated by mutations that changed the normal patterns of flower development. He showed that those mutations created sepals (the green parts that typically lie under the petals) instead of the normal petals or even leaves instead of flowers. Meyerowitz wondered what was going on.
The answer, Meyerowitz’s lab found, lay in three classes of genes—dubbed A, B, and C—which controlled the floral pattern. Turning on genes in classes A and B made a petal, for instance, while genes of classes A and C together resulted in a stamen. But if none of the three gene groups was working, then the plant didn’t make floral organs at all; it made flowers in which all the organs were leaves instead. This finding suggested that, in the course of evolution, plants “figured out” how to turn the basic blueprint of leaves into the flowers we see today through the effect of such genes. The discovery and similar ones made by colleagues “began to reveal the logic of development,” says Meyerowitz.
By the early 1990s, Meyerowitz had given up his fruit fly research. “The Drosophila world seemed to be in good hands, and we were having so much more fun with the plant stuff,” he says. Then a major project “fell into my lap,” he says. His postdoc, Tony Bleecker, had created mutant Arabidopsis plants when he was a graduate student that were unresponsive to ethylene, a key plant hormone that affects many aspects of development, including flower opening and leaf loss. Bleecker and Caren Chang, a graduate student and, later, postdoc in the Meyerowitz lab, then isolated the gene that was mutated; it was the first receptor gene ever cloned for a plant hormone. Surprisingly, the receptor was a histidine kinase gene of a type previously found only in bacteria. Where could a plant get such a gene? The most likely route, researchers suspect, is that the gene originally came from a cyanobacteria that lived in symbiosis with ancestral plants, enabling them to grab energy from the sun in what became photosynthesis. These bacteria are thought to have become the chloroplasts, which perform the process of photosynthesis in today’s plants.
The find opened the door to understanding how the whole system of plant hormones works—a bit “like opening Chapman’s Homer,” says Meyerowitz, in reference to the famous poem by John Keats. Now, he’s using live imaging and mathematical modeling, among other tools, to probe how cells use a ubiquitous hormone named auxin to communicate and how cells in the growing tip of a plant, the apical meristem, differentiate into leaves, flowers, grains, and fruits.
The work already has revealed how cells respond to mechanical stress, for instance, and overturned a basic doctrine of plant regeneration—that all plant cells have the ability to regenerate a whole new plant. Instead, Kaoru Sugimoto, a postdoc in Meyerowitz’s lab, found that regeneration is made possible by a population of adult stem cells.
The mustachioed Meyerowitz is proud of his lab’s accomplishments, especially because “we’ve been doing this on a starving budget all these years,” he says. But he’s equally proud of the many students and postdocs whose careers he has nurtured. In typical fashion, he gives them most of the credit. “I just sat back and watched while they did the work,” he says.