Biochemistry

Abstract

CS-1-2 - Putative Plastid Rhomboid Protease Plays a Role in Phosphatidate Metabolism in Arabidopsis thaliana

Sunday, July 15
1:23 PM - 1:43 PM

The thylakoid membranes of the chloroplast house the photosynthetic machinery that converts light into chemical energy. Chloroplast membranes are unique from other plant organelles in their lipid makeup, which is dominated by mono and digalactosyldiacylglycerol (MGDG and DGDG). The predominant galactolipid, MGDG, can be made through both plastidic (prokaryotic) and ER (eukaryotic) pathways in Arabidopsis, resulting in two distinct species of lipid. Phosphatidate has been shown to be the first acylated lipid species in the plastid galactolipid biosynthetic pathway, providing a pool of diacylglycerol for MGDG Synthase. The enzymatic reactions yielding these galactolipids have been well-described, however, regulation of these steps is unknown at this time. Intramembrane proteolysis, as demonstrated by members of the rhomboid-like family of proteins, is one example of regulation through proteolysis. One such rhomboid-like protein 10 (RBL10), found in the chloroplasts of Arabidopsis thaliana, may be involved in maintaining biosynthesis of MGDG through the plastidic pathway. Plants disrupted in the gene encoding RBL10 have greatly decreased 16:3 and increased 18:3 acyl chain abundance in MGDG in leaves. Additionally, rbl10 mutants show reduced 14C – acetate incorporation into MGDG during the first hour of pulse-chase labeling, indicating a reduced flux through the prokaryotic galactolipid biosynthesis pathway. While plastid MGDG biosynthesis is reduced in rbl10 mutants, they are capable of synthesizing PA, as well as making normal amounts of MGDG by compensating with ER lipid precursors. Though the molecular mode of action remains to be described, these preliminary findings link this protease to utilization of PA for galactolipid biosynthesis and give an opportunity to characterize a novel lipid regulatory mechanism.


 

Co-Authors

John Froehlich – Michigan State University; Olivia Baylis – Michigan State University; Anthony Rotondo – Michigan State University; Christoph Benning – Michigan State University

Anastasiya Lavell

Graduate Student
Michigan State University

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Send Email for Anastasiya Lavell


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CS-1-2 - Putative Plastid Rhomboid Protease Plays a Role in Phosphatidate Metabolism in Arabidopsis thaliana



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