Deficiency in Phosphatidylserine Decarboxylase Activity in the psd1 psd2 psd3 Triple Mutant of Arabidopsis Affects Phosphatidylethanolamine Accumulation in Mitochondria

Abstract

Phosphatidylserine (PS) decarboxylase is involved in the synthesis of the abundant phospholipid phosphatidylethanolamine (PE), particularly in mitochondria, in many organisms, including yeast (Saccharomyces cerevisiae) and animals. Arabidopsis (Arabidopsis thaliana) contains three genes with sequence similarity to PS decarboxylases, and the respective gene products were functionally characterized after heterologous expression in yeast and Escherichia coli. While the PSD1 protein localizes to mitochondria, PSD2 and PSD3 are found in the endomembrane system. To study the role of PSD genes in plant phospholipid metabolism, Arabidopsis insertional mutants for psd1, psd2, and psd3 were obtained. The single mutants were decreased in PS decarboxylase activity to various extents, but mutant plants showed no obvious growth or morphological phenotype. A triple mutant, psd1 psd2 psd3, was generated that was totally devoid of PS decarboxylase activity. While the phospholipid composition in whole leaves was unchanged, the PE content in isolated mitochondria of psd1 psd2 psd3 was decreased. Therefore, the predominant proportion of PE in Arabidopsis is synthesized by alternative pathways, but a significant amount of mitochondrial PE is derived from the PS decarboxylase reaction. These results imply that, similar to yeast and animal cells, a specific phospholipid transfer from the endoplasmic reticulum to mitochondria exists in plants.

Role of Aminoalcoholphosphotransferases 1 and 2 in Phospholipid Homeostasis in Arabidopsis

“…A previous report suggests that PS in plants was not a significant source of PE production. For instance, a triple mutant of Arabidopsis PS decarboxylases only had a mild decrease of PE in mitochondria (Nerlich et al, 2007). On the other hand, we observed an increase in PE species with long-chain fatty acids in AAPT KO/RNAi lines, and PS contains a higher percentage of long-chain FAs than other species.…”

Phosphatidylethanolamine Synthesis in the Parasite Mitochondrion Is Required for Efficient Growth but Dispensable for Survival of Toxoplasma gondii

“…The CDP-ethanolamine route is reported to be essential in protozoan parasites, Plasmodium and Trypanosome species (41, 43, 44). Conversely, Arabidopsis and Saccharomyces can tolerate a collective ablation of their PSD proteins or the CDP-ethanolamine pathway (11,40). Interestingly, both of these routes are not mutually exclusive in T. gondii, and a specific lipid transfer appears to exist between the parasite mitochondrion and ER.…”

ArabidopsisPhosphoglycerate Dehydrogenase1 of the Phosphoserine Pathway Is Essential for Development and Required for Ammonium Assimilation and Tryptophan Biosynthesis

“…Ser is an important amino acid that is an essential constituent of proteins, and is also a substrate for the biosynthesis of phosphatidylserine (Vance and Steenbergen, 2005;Nerlich et al, 2007), Trp (Tzin and Galili, 2010), and Trp-derived secondary metabolites such as auxin, indolic glucosinolates, and camalexin (Glawischnig et al, 2000;Gigolashvili et al, 2007;Sazuka et al, 2009;Vernoux et al, 2010). Furthermore, Ser functions as an important single-carbon (C1) donor in tetrahydrofolate (THF) metabolism in plants (Hanson and Gregory, 2002;Rébeillé et al, 2007).…”