ALA10, a Phospholipid Flippase, Controls FAD2/FAD3 Desaturation of Phosphatidylcholine in the ER and Affects Chloroplast Lipid Composition in Arabidopsis thaliana

Abstract

The biogenesis of photosynthetic membranes relies on galactoglycerolipids, which are synthesized via pathways that are dispatched over several cell compartments. This membrane biogenesis requires both trafficking of lipid intermediates and a tight homeostatic regulation. In this work, we address the role of ALA10 (for aminophospholipid ATPase), a P 4 -type ATPase, in a process counteracting the monogalactosyldiacylglycerol (MGDG) shortage in Arabidopsis (Arabidopsis thaliana) leaves. ALA10 can interact with protein partners, ALIS1 (for ALA-interacting subunit1) or ALIS5, leading to differential endomembrane localizations of the interacting proteins, close to the plasma membrane with ALIS1 or to chloroplasts with ALIS5. ALA10 interacts also with FATTY ACID DESATURASE2 (FAD2), and modification of ALA10 expression affects phosphatidylcholine (PC) fatty acyl desaturation by disturbing the balance between FAD2 and FAD3 activities. Modulation of ALA10 expression downstream impacts the fatty acyl composition of chloroplast PC. ALA10 expression also enhances leaf growth and improves the MGDG-PC ratio, possibly through MGDG SYNTHASE1 (MGD1) activation by phosphatidic acid. The positive effect of ALA10 on leaf development is significant in conditions such as upon treatment of plants with Galvestine-1, an inhibitor of MGDG synthases, or when plants are grown at chilling temperature.

A predicted plastid rhomboid protease affects phosphatidic acid metabolism in Arabidopsis thaliana

“…To describe this system, it seems instructive to draw parallels with the ER phospholipid transporter ALA10, which is reported to form a complex with the ER desaturases FAD2/FAD3 to modulate the balance between PC and MGDG (Botella et al ., ). Therefore, it seems plausible that a PA transporter could be in a complex with the plastid PA biosynthetic enzymes and possibly even the PAP, resulting in substrate channeling.…”

Reorganization of Acyl Flux through the Lipid Metabolic Network in Oil-Accumulating Tobacco Leaves

“…3C) is also consistent with an increased rate of acyl flux through PC, because membrane lipid desaturation is dependent on both the rate of desaturation and the rate of acyl flux through the membrane lipid. Increases in the fatty acid synthesis rate have been demonstrated to increase 18:1 and decrease PUFA content of membrane lipids (Maatta et al, 2012;Meï et al, 2015;Botella et al, 2016). Considering that the engineering of a very large pull of acyl chains into TAG in the HO line only increases PC acyl editing instead of drawing acyl chains away from it, PC acyl editing may be considered a key part of fatty acid export from the plastid into the eukaryotic pathway.…”

Using lipidomics for expanding the knowledge on lipid metabolism in plants

“…When absent, its lipid substrates accumulate and induce growth, resulting in faster-growing plants [55]. The flippase ALA10, the former a group of membrane-bound ATPase transporters that move lipids from one leaflet of the membrane to the other, and its control of FAD2/3, two fatty-acid desaturases-enzymes turning single bonds into double bonds in fatty acids, were analyzed and shown to also affect chloroplast lipid composition [56]. PLA 2 , a phospholipase-enzymes separating fatty acids from glycerophospholipids-was analyzed in its contribution to the high production of an industrially valuable hydroxy fatty acid in castor plants [57].…”