Location: Plant Physiology and Genetics ResearchTitle: Arabidopsis GPAT9 contributes to synthesis of intracellular glycerolipids but not surface lipids
|SINGER, STACY - University Of Alberta|
|CHEN, GUANQUN - University Of Alberta|
|MIETKIEWSKA, ELZBIETA - University Of Alberta|
|JAYAWARDHANE, KETHMI - University Of Alberta|
|WESELAKE, RANDALL - University Of Alberta|
Submitted to: Journal of Experimental Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/12/2016
Publication Date: 6/20/2016
Citation: Singer, S.D., Chen, G., Mietkiewska, E., Tomasi, P., Jayawardhane, K., Dyer, J.M., Weselake, R.J. 2016. Arabidopsis GPAT9 contributes to synthesis of intracellular glycerolipids but not surface lipids. Journal of Experimental Botany. doi: 10.1093/jxb/erw242.
Interpretive Summary: The seed oils of plants are important agricultural commodities that are used for both food applications and as a substitute for dwindling petrochemical reserves in the form of renewable feedstocks for the production of biodiesel and industrial chemicals. The demand for plant oils is increasing, and there is a substantial amount of research being conducted to increase oil production in plants. Achieving this goal, however, is dependent in part on developing a thorough working knowledge of the molecular mechanisms involved in seed oil production. Biochemical studies have revealed that production of oil involves three key steps, whereby three fatty acids are consecutively attached to a glycerol backbone to form a “triacylglycerol”, which is the major component of all plant oils. While this pathway was initially identified over 50 years, and the enzymes for steps two and three of fatty acid attachment are known, the enzyme catalyzing the first step of oil synthesis remains unknown. Scientists at the University of Alberta, Edmonton, Alberta, Canada, in collaboration with ARS scientists at the US Arid-Land Agricultural Research Center in Maricopa, Arizona, have characterized a glycerol-3-phosphate acyltransferase that catalyzes this first step of oil synthesis. By using both gene over-expression studies, as well as gene knockouts, the scientists show that this gene directly affects soil oil content and composition. These results fill a key gap in our knowledge of oil production and will be important to scientists interested in increasing oil content in crop plants.
Technical Abstract: GLYCEROL-3-PHOSPHATE ACYLTRANSFERASE (GPAT) genes encode enzymes involved in glycerolipid biosynthesis in plants. Ten GPAT homologues have been identified in Arabidopsis thaliana (Arabidopsis). GPATs 4-8 have been shown to be involved in the production of extracellular lipid barrier polyesters. Recently, GPAT9 was reported to be essential for triacylglycerol (TAG) biosynthesis in developing Arabidopsis seeds. The enzymatic properties and possible functions of GPAT9 in surface lipid, polar lipid and TAG biosynthesis in non-seed organs, however, have not been investigated. Here we show that Arabidopsis GPAT9 exhibits sn-1 acyltransferase activity with high specificity for acyl-coenzyme A, thus providing further evidence that this GPAT is involved in storage lipid biosynthesis. We also confirmed a role for GPAT9 in seed oil biosynthesis and further demonstrate that GPAT9 contributes to the biosynthesis of both polar lipids and TAG in developing leaves, as well as lipid droplet production in developing pollen grains. Conversely, alteration of GPAT9 expression had no obvious effects on surface lipid biosynthesis. Taken together, these studies expand our understanding of GPAT9 function to include modulation of several different intracellular glycerolipid pools in plant cells.