Antje Heese, MU assistant professor of biochemistry and a member of the Interdisciplinary Plant Group, identified the protein, known as SCD1, while searching for proteins that interact with a specific receptor protein on the plant cell's surface, called FLS2. When FLS2 detects invading bacterial pathogens, it signals the cell to initiate several defense responses that restrict bacterial growth.
Through a series of experiments in the model plant Arabidopsis thaliana, Heese and her colleagues demonstrated that SCD1 is required for some, but not all, FLS2-initiated defense responses. Importantly, when exposed to a bacterial pathogen, plants with less SCD1 protein were more resistant to infection than normal plants.
The researchers also demonstrated that the protein's function in immunity is independent of its function in growth and development.
"There are only a few examples in plants where two separable functions, one in defense and one in growth and development, have been demonstrated," Heese said.
In its role in growth and development, SCD1 is involved in producing the pores that allow leaves to exchange water, oxygen, and carbon dioxide. Previous studies suggest that SCD1 helps to ensure that materials arrive at the right place on the cell surface for normal pore development. Heese believes the protein may play a similar role in disease resistance.
"SCD1 may be important for making sure the components of the defense response are located at their correct sites inside the cell. If they're not transported to their correct site, they don't function," Heese said.
In their studies, Heese and colleagues identified a specific segment of SCD1 that is important for its functions in defense responses. This segment, called the DENN domain, is also found in proteins implicated in human neurological diseases, including Alzheimer's. The discovery that the DENN domain has a function in plant immunity may lead to new discoveries in human diseases.
The study "Novel functions of STOMATAL CYTOKINESIS-DEFECTIVE 1 (SCD1) in innate immune responses against bacteria" appears in the July 23 issue of the Journal of Biological Chemistry.
Other MU researchers contributing to the study include David A. Korasick, lead author and research technician in biochemistry; Katie A. Walker, formerly an undergraduate student research assistant in biochemistry and now research technician at Monsanto Corporation; and Jeffrey Anderson, a postdoctoral researcher in biochemistry. Sebastian Y. Bednarek, associate professor of biochemistry at the University of Wisconsin, Madison, and his graduate student, Colleen McMichael, also contributed to the work.
Source: University of Missouri