The Missing Piece: Understanding the hothead protein’s role in plant cuticle formation

Thursday, January 12, 2017

Eric Le Dreff-Kerwin looks at a protein structure on a laptop.

Byline: Quinn Abrams, Biology MSc student

Missing a single protein can have lethal consequences for plants. Cuticles are the waxy wall that protects plants from sunlight, pesticides, and dehydration. But damage to the cuticle, like when the Hothead protein is missing, causes the wall to fall down.

Éric Le Dreff-Kerwin, a Biology master’s student at the University of Waterloo under the supervision of Profs. Susan Lolle and Todd Holyoak, is studying the structure of the protein Hothead and its mutant forms in the plant Arabidopsis thaliana.

We want to know the structure of Hothead and its mutants [in order to] understand the role of the protein in cuticle malformation.

The cuticle is the waxy layer found on the outside of above ground portions of the plant, and when it is compromised, the plant is not able to defend itself against ultraviolet light, pests, or dehydration. It is not known at which stage of cuticle development the Hothead protein is needed, but it is likely involved in converting one of the raw materials that make up the protective wall into its finished product.

While the function and structure of Hothead are currently unknown, all 11 known mutant strains have some degree of cuticle malformation.

Presently, there are some predictions of the protein’s structure and function, based on  similarities in the primary sequence of hothead and two other proteins families; mandelonitrile lyases, and omegahydroxy-dehydrogenases.

Once you’re able to isolate a protein and determine its structure, it opens up a world of possibilities.

In order to solve the protein structures of Hothead and its mutant forms, Le Dreff-Kerwin’s first step will be to produce large amounts of the protein in bacteria, and then isolate it through a separation technique known as liquid chromatography.

Once there is a large enough stock of the Hothead protein, the structure can be determined by making crystals of the protein, and then analyzing the diffraction patterns that result when the crystals are exposed to a high intensity x-ray beam.

The same process will be used to determine the structure of some of the known mutants of hothead that cause defects in cuticle formation. Additionally, he will use the protein in various enzymatic tests to elucidate its enzymatic activity and illuminate its exact function.

Le Dreff-Kerwin hopes that by determining the structure of the protein and how it functions, he will be able to better understand the role of the Hothead protein in cuticle formation.

NOTE: BIOL 690 Scientific Communication is a graduate course that helps students enhance their skills in the acquisition, organization and presentation of scientific information. Students in the course interviewed and wrote a news story about one of their classmates' research.

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