Barley Cer-q encodes a lipase involved in the synthesis of epicuticular waxes

Abstract: A plant’s rain coat Imagine yourself taking a walk on a cloudy day. Suddenly, the sky opens and the rain is pouring down making you totally soaked. Now imagine that you predicted that it would start to rain so you put on a rain coat. When the rain starts to fall, you won’t get wet since the rain drops will strike against the rain coat and get drained. In the same manner, the wax on plants is protecting it from being drowned. Wax form a thin hydrophobic layer that covers almost all areal surfaces of the plant and is needed in order for the plant to survive. Beside the waterresistant properties, wax protects the plant from the dangerous beams of the sun and possibly infectious microorganisms. Wax is composed of very long chain aliphatics as alcohols and fatty acids and can be seen as a glossy film on the surface of tomatoes and rose blades or as a damp blue/grey shimmer on cereals such as barley. What is special for the wax of barley is the presence of aliphatics named β-diketones, hydroxy-β-ketones and esterified alkan-2-ols and constitutes of almost fifty percent of the total wax load. The process at which these aliphatics are synthesised has been studied for almost forty years. It is known that the genes that determine the formation and deposition of wax in barley is the eceriferum (cer) genes where the cer-cqu genes encodes for proteins that take part in the formation of β-diketones, hydroxy-β-ketones and esterified alkan-2-ols found on the uppermost leaf sheet, internodes and spike of wild-type barley. However, where these genes are located on the chromosome arm and what type of proteins they encode for have been an enigma, but earlier this year was a study presented that might have answered these questions. I´ve studied one of these proteins, namely Cer-q, presented in the study. This protein is thought to play a very important role in the beginning of the synthesis due to the fact that plants lacking this protein do not form either β-diketones, hydroxy-β-ketones or esterified alkan-2-ols. Cer-q is thought to be a lipase based on its resemblance to other known lipases. The objective for my research was therefore to test and see if Cer-q in fact has lipase activity and in order to achieve this, I had to produce and purify Cer-q. My results showed that this is a protein that can be produced in large volumes at high concentration. I also got results that indicate that Cer-q in fact preform lipase activity. Barley is today the second largest crop after wheat in Europe and is used to produce flour and grain and is the main ingredient in beer, though half of the production is actually used for animal feed. The development of wax on the crop is essential for a good harvest and in understanding the biochemical process of how it is created we could increase the yield and by that feed more people. Supervisor: Mats Hansson Bachelor´s Degree Project 15 credits in Molecular Biology Department of Biology, Lund University