Arabidopsis cytosolic acyl‐CoA‐binding proteins function in determining seed oil composition

Abstract

As plant seed oils provide animals with essential fatty acids (FAs), genes that regulate plant lipid metabolism have been used in genetic manipulation to improve dietary seed oil composition and benefit human health. Herein, the Arabidopsis thaliana cytosolic acyl‐CoA‐binding proteins (AtACBPs), AtACBP4, AtACBP5, and AtACBP6 were shown to play a role in determining seed oil content by analysis of atacbp (atacbp4, atacbp5, atacbp6, atacbp4atacbp5, atacbp4atacbp6, atacbp5atacbp6, and atacbp4atacbp5atacbp6) seed oil content in comparison with the Col‐0 wild type (WT). Triacylglycerol (TAG) composition in electrospray ionization‐mass spectrometer (ESI‐MS) analysis on atacbp6 seed oil showed a reduction (−50%) of C58‐TAGs in comparison with the WT. Investigations on fatty acid composition of atacbp mutants indicated that 18:2‐FA accumulated in atacbp6 and 18:3‐FA in atacbp4, both at the expense of 20:1‐FA. As TAG composition can be modified by acyl editing through phosphatidylcholines (PC) and lysophosphatidylcholines (LPC), total PC and LPC content in atacbp6 mature seeds was determined and ESI‐MS analysis revealed that LPC had increased (+300%) at the expense of PC. Among all the 14 tested PC species, all (34:1‐, 34:2‐, 34:3‐, 34:4‐, 34:5‐, 34:6‐, 36:2‐, 36:3‐, 36:5‐, 36:6‐, 38:2‐, 38:3‐, and 38:4‐PCs) but 36:4‐PC were lower in atacbp6 than the WT. In contrast, all LPC species (16:0‐, 18:1‐, 18:2‐, 18:3‐, and 20:1‐LPC) examined were elevated in atacbp6. LPC abundance also increased in atacbp4atacbp5, but not atacbp4 and atacbp5. Interestingly, when LPC composition in atacbp4atacbp5 was compared with atacbp4 and atacbp5, significant differences were observed between atacbp4atacbp5 and each single mutant, implying that AtACBP4 and AtACBP5 play combinatory roles by affecting LPC (but not PC) biosynthesis. Furthermore, PC‐related genes such as those encoding acyl‐CoA:lysophphosphatidylcholine acyltransferase (LPCAT1) and phospholipase A2 alpha (PLA2α) were upregulated in atacbp6 developing seeds. A model on the role of AtACBP6 in modulating TAG through regulating LPCAT1 and PLA2α expression is proposed. Taken together, cytosolic AtACBPs appear to affect unsaturated TAG content and are good candidates for engineering oil crops to enhance seed oil composition.

Synaptotagmins Maintain Diacylglycerol Homeostasis at Endoplasmic Reticulum-Plasma Membrane Contact Sites during Abiotic Stress

“…Lipids were dried by adding gas N 2 . Quantitative analyses of lipids (at Rothamsted Research, UK), including neutral (diacylglycerols, DAG) and polar lipids (phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylinositol (PI), phosphatidylglycerol (PG), Lysophosphatidylcholine (LPC), monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG)) lipids were carried out using electrospray ionization tandem triple quadrupole mass spectrometry (API 4000 QTRAP; SCIEX; ESI-MS/MS) as described previously (Guo et al, 2019). The internal standards were supplied by Avanti (Alabama, USA), incorporated as 8 pmol 13:0-LPC, 0.086 nmol di24:1-PC, 0.080 nmol di14:0-PE, 0.05 nmol di18:0-PI, 0.080 di14:0-PG, 0.03 nmol di18:0-PS and 0.03 nmol di14:0-PA.…”

Functional Role of Long-Chain Acyl-CoA Synthetases in Plant Development and Stress Responses

“…These results demonstrate that LACSs display conserved roles in TAG synthesis in the identified plant species, but we cannot ignore that TAG FA compositions vary among species. For example, oleic acids are the predominant FA constituent of TAG in rapeseed oil, whereas linoleic acids dominate Arabidopsis seed oil ( Guo et al, 2019 ; Ding et al, 2020 ). As such, to precisely interpret the function of each LACS in TAG biosynthesis, multiple factors need to be considered, including plant species, substrate preference, tissue expression pattern, subcellular localization, and protein-level interactions with other enzymes involved in TAG synthesis.…”

Lipids Composition in Plant Membranes

“…The core building block of fatty acids is a hydrocarbon chain with a carboxyl group (-COOH) located on its terminal end. Based on the chain length of fatty acids, they are classified as: short-chain (aliphatic tails of up to 5 or even 7 carbons), medium-chain (aliphatic tails of 6-8 up to 12-14 carbons), long-chain (aliphatic tails of 13-18 up to 22 carbons), or very long-chain fatty acids (aliphatic tails longer than 22 carbons; >C22) [17][18][19][20][21]. Most often, the number of carbon atoms in the plant tissues is between 14 and 24.…”