Johal and his colleagues found that loss of a gene product called a p-glycoprotein generates these dwarf corn and sorghum plants by interfering with the movement of auxin, an essential hormone in plant growth and development. They also have identified the genetic mechanism that causes dwarf sorghum plants to spontaneously revert to a taller form.
In corn, the normal gene Br2 produces a p-glycoprotein, and the researchers found that a mutation in this gene is responsible for the altered growth of the dwarf plant. They also found that the dwarf mutants, while shorter than their taller counterparts, have more cells per unit area in the stalk, which makes the stalks stronger and perhaps more effective at retaining water.
Although p-glycoproteins are involved in transporting molecules across cell membranes, their exact function still has not been conclusively shown.
"This finding in br2 dwarf mutants demonstrates the 'real-world' impact of research involving model plants," said Angus Murphy, assistant professor of horticulture and a collaborator on the study. Murphy recently demonstrated that in Arabidopsis, a plant commonly used as a model system in plant genetics and molecular biology, mutations in a p-glycoprotein gene similar to Br2 disrupt auxin flow, leading to alteration of the plant's form.
"After discovering that p-glycoproteins control hormonal movement in Arabidopsis, we were able to apply that information to demonstrate that the same mechanism underlies a well-described phenomenon in corn," Murphy said. "The kind of collaboration that produced this discovery is one of the unique characteristics of the Purdue research environment."
Johal and Murphy work in different academic departments located in different buildings - but they both agree that the combination of their diverse areas of expertise was key to their success.