Configuration of the sugar head of glycolipids in thylakoid membranes

Abstract

Glycolipids constitute the majority of membrane components in oxygenic photosynthetic organisms, whereas they are minor lipids in other organisms. In cyanobacteria, three glycolipids comprise ~90 mol% of the total lipids in thylakoid membranes, where photosynthetic electron transport occurs. Among these glycolipids, 80 mol% are galactolipids (monogalactosyldiacylglycerol and digalactosyldiacylglycerol). Galactolipids are well conserved in oxygenic photosynthetic organisms and are believed to be essential for the integrity of the membrane system. It remains unclear, however, which part(s) of the galactolipid structure is the key factor for their function, e.g., the sugar moiety and/or the anomeric configuration. To address this issue, several bacterial membrane glycolipid synthase genes have been introduced into cyanobacteria to test for complementation of knocked-out genes involved in galactolipid biosynthesis. In this review, we summarize recent advances in the analyses of sugar species and configurations of glycolipids heterologously synthesized in the thylakoid membrane and discuss their functional importance.4

Origin of cyanobacterial thylakoids via a non-vesicular glycolipid phase transition and their impact on the Great Oxygenation Event

“…It is very important to note that the relative MGDG/DGDG ratio differs in the two membrane domains: this indicates that although DGDG is produced from MGDG, some regulatory mechanisms uncouple its final proportion from the available amount of substrate. This is consistent with the multitude of roles played by DGDG which need to be finely controlled, including the stability of the photosynthetic machinery Apdila and Awai, 2018;Sakurai et al, 2007;Awai et al, 2007). The MGDG-rich domains at the plasma membrane appear therefore as ideal platforms to promote HexII  Lm phase transition.…”

“…The activity converting MGlcDG into MGDG in Gloeobacter was measured (Sato, 2015), but the corresponding enzyme is still uncharacterized molecularly. It was tentatively called MgdX (Apdila and Awai, 2018). MGlcDG does not accumulate and this lipid is barely detected in Gloeobacter, in support of a physical proximity between MgdA and MgdX in vivo.…”

“…The galactolipid biosynthesis pathway in Gloeobacter was shown to be similar to that in all other Cyanobacteria. Firstly MGlcDG is produced by a monoglucosyldiacylglycerol synthase (MgdA) (Apdila and Awai, 2018;Awai et al, 2006), then the glucosyl polar head is epimerized by an unknown mechanism into a galactosyl residue, thus forming MGDG; eventually DGDG is formed by the action of a digalactosyldiacylglycerol synthase (DgdA) similar to that identified in other Cyanobacteria (Apdila and Awai, 2018;Sakurai et al, 2007;Awai et al, 2007). The activity converting MGlcDG into MGDG in Gloeobacter was measured (Sato, 2015), but the corresponding enzyme is still uncharacterized molecularly.…”

Brassinosteroids and the Tolerance of Cereals to Low and High Temperature Stress: Photosynthesis and the Physicochemical Properties of Cell Membranes

“…Because the plasmalemma is important in the process of acclimation to temperature, this direction of changes could be one of the many reasons for the lower tolerance of the mutants to frost and a higher tolerance to heat stress [ 13 ]. On the other hand, a reverse effect is observed in the case of the monogalactolipid fraction (more characteristic for the chloroplast membranes [ 127 , 128 ]) compared to the phospholipid fraction. In the BR mutants at 5 °C, 18:3 was higher (and fluidity as well) while at 27 °C (and 20 °C), it was lower (together with a decreased fluidity, which was expressed by A lim ).…”

Solid Matrix-Supported Supercritical CO2 Enhances Extraction of γ-Linolenic Acid from the Cyanobacterium Arthrospira (Spirulina) platensis and Bioactivity Evaluation of the Molecule in Zebrafish

“…As GLA accounted for as high as 30% of total fatty acids (TFAs) in A. platensis cells [16], and α-linolenic acid (the isomer of GLA) was absent in TFAs [15], isolation, and purification of GLA-containing glycolipids from A. platensis could be cost-effective. In cyanobacteria glycolipids, 80 mol% are galactolipids [17], which contain the various fatty acid acyl groups (e.g., GLA) that are important for their functions. Although marine cyanobacteria represent an untapped natural source of glycolipids for pharmaceutical and nutraceutical applications, knowledge aboutcyanobacteria-derived glycolipids is rather limited.…”