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CSULB Botanist Helps Discover Gene That Regulates Corn Growth

Published: November 17, 2008

A team of U.S. researchers including Simon Malcomber, an assistant professor and evolutionary botanist in the Department of Biological Sciences at CSULB, has discovered a gene that helps regulate the growth of corn, or maize.

Their findings appeared in an article in the Sept. 30 edition of the Proceedings of the National Academy of Sciences (www.pnas.org), titled “Sparse inflorescence1 encodes a monocot-specific YUCCA-like gene required for vegetative and reproductive development in maize.”

They learned that the sparse inflorescence1 (spi1) gene helps control an important plant hormone called auxin. “Auxin is involved in the regulation of many aspects of plant growth—the formation of leaves, branches and flowers, anything which is coming off the side of a plant stem,” Malcomber said. “When we think of it in terms of crops, you can think of leaf vegetables, and auxin is going to be involved in the production of those leaves. In terms of the maize research that we published here, any gene that regulates auxin is going to be playing a direct role in crop yield.”

Malcomber worked with Andrea Gallavotti, Darren Hall and Robert J. Schmidt of UC San Diego; Solmaz Barazesh and Paula McSteen of Pennsylvania State University; and David Jackson of Cold Spring Harbor Laboratory in New York.

Malcomber is interested in how the gene evolved, so the team did a genetic comparison.

“What’s interesting from our perspective is that there is a group of genes called YUCCA which were first described from another plant called Arabidopsis, which is the preeminent plant model system,” he said. “What we’ve shown with sparse inflorescence1 is that it’s actually quite distantly related to the Arabidopsis genes. It’s all part of the same gene family, but they’ve undergone separate radiations. The genes have duplicated in different parts of the flowering plant tree of life.

“What we’ve shown from the evolutionary analyses that we have in this paper is that sparse inflorescense1 is a gene that is only found in monocot plants—onions, lilies, palms, grasses and gingers,” he continued. “It’s only very distantly related to the YUCCA genes that are found in Arabidopsis. Related to that, it has a very different role. If we look at YUCCA genes in Arabidopsis, if you take one of them away, it doesn’t do much in terms of affecting the way the plant is growing. You have to take away at least three of those genes to see a difference in how the plant appears. If you take the sparse inflorescence1 gene away, it has a profound effect on the way the plant appears,” leading to stunted growth.

“What’s interesting from my perspective as a plant evolutionary biologist is that we’re looking at the way that the genes make plants appear different from other plants,” he said. “Within the grasses, which is our major focal group, this maize gene is acting differently than what is being described in rice. Maize and rice are quite distantly related within the grasses but it does suggest that there has been a change in the function of this gene within the diversification of the grass family.”

Other major grass crops include barley, oats, wheat, teff and sorghum. “These are all important crop species, so we still have to find out how sparse inflorescence is regulating the growth in those species,” he said.

Dr. Simon Malcomber

Photo by Victoria Sanchez
Simon Malcomber (r) working with a student.

To continue their studies, Malcomber and several team members, along with additional researchers from Penn State and UC San Diego, recently received a $4.75 million grant from the National Science Foundation Plant Genome program. CSULB will receive $806,000 of those funds.

“We’re going to investigate the genes that are involved in regulating this plant hormone auxin during shoot growth, which is the above-ground portion of the plant. Most of the auxin research has focused on the root and relatively little has focused on the shoot itself,” Malcomber said. “We’re trying to test some of the hypotheses that they’re generating with maize and Arabidopsis to see how broadly they can be applied across all flowering plants to see whether or not these mechanisms also apply in sugar cane, onions, cabbages and other crops as well. We’re trying to test these hypotheses to see if these same genes are functioning in the same way to regulate crop yields in diverse species.”

Their work has practical value, Malcomber explained. “We’re doing the basic research that is essential to be able to manipulate these genes as need be by the agricultural industry to improve crop yield and come up with novel biofuels as well. So, perhaps there are certain plants that aren’t producing enough leaf material, but if we know that we can manipulate some of these genes which actually increase the number of leaves that are going to be produced, then that is going to have a downstream effect in terms of coming up with novel biofuels.”

The grant also will provide educational experiences for high school as well as college undergraduate, graduate and postdoctoral students, Malcomber added. The team plans to include results of the new study to the Botanical Society of America’s “Planting Science” educational program and Web site.