Mono‐ and digalactosyldiacylglycerol composition of the marennine‐producing diatom, Haslea ostrearia: Comparison to a selection of pennate and centric diatoms

Abstract

Summary Diatoms are one of the largest groups of primary producers in the oceans, yet despite their environmental importance little is known about their plastidial lipid biochemistry. It has been previously reported that Skeletonema species contain primarily C16/C16 and C20/C16 forms of mono‐ and digalactosyldiacylglycerol (MGDG and DGDG, respectively). Likewise, it was also reported that Phaeodactylum tricornutum contains primarily C16/C16 and C20/C20 forms of MGDG and DGDG. We seek to relate their studies to other diatoms, both in the centrics and pennates, with particular focus on the marennine‐producing pennate diatom, Haslea ostrearia. To this end, the composition and positional distribution of fatty acids of MGDG and DGDG were examined using positive‐ion electrospray ionization/mass spectrometry (ESI/MS). Two centric diatoms, Skeletonema marinoi and Thalassiosira weissflogii, and the pennate diatom, P. tricornutum, contained primarily C20/C16 (sn‐1/sn‐2) and C18/C16 forms of MGDG and DGDG. The other pennate diatoms, H. ostrearia and Navicula perminuta, contained primarily C18/C16 or C18/C18 forms of MGDG and DGDG, indicating a previously unrecognized fatty acid diversity in diatom MGDG and DGDG.

Lipid Dependence of Xanthophyll Cycling in Higher Plants and Algae

“…Besides the C20/C16 forms of MGDG, MGDG molecules with C16 FAs at both the sn-1 and sn-2 position can be observed. DGDG exhibits a comparable FA composition to MGDG and is also enriched in EPA (Yongmanitchai and Ward, 1993;Yan et al, 2011;Dodson et al, 2013Dodson et al, , 2014. Like in the MGDG molecule EPA usually occupies the sn-1 position of DGDG while at the sn-2 position C16 FAs are observed.…”

“…As it has been demonstrated for MGDG, DGDG forms with C16 FAs at both the sn-1 and sn-2 positions can be found and DGDG with C20:5 and C16:3 seems to represent the most abundant diatom DGDG molecule. Earlier studies have reported that a difference exists in the FA composition of centric and pennate diatoms and that in the pennate diatoms EPA is replaced by C18 FAs in the MGDG and DGDG molecules (Dodson et al, 2013). However, more recent studies have indicated that the differences in the FA composition of MGDG and DGDG of centric and pennate diatoms may be related to differences in their reaction to environmental temperatures and that EPA is present at lower temperatures and may be replaced by C18 FAs at higher temperatures (Dodson et al, 2014).…”

“…In diatoms MGDG contains the main long-chain FA of diatoms, i.e., eicosapentaenoic acid (EPA, 20:5, Yongmanitchai and Ward, 1993;Yan et al, 2011;Dodson et al, 2013;Dodson et al, 2014). EPA is preferentially bound to the sn-1 position of the glycerol backbone whereas the sn-2 position is usually occupied by C16 FAs with varying degrees of unsaturation (16:1, 16:2, 16:3, 16:4).…”

The lipid biochemistry of eukaryotic algae

“…However, it is also relevant to a study in diatoms where MGDG and DGDG molecular species were compared in two centric species (Skeletonema marinoi, Thalassiosira weissflogii) with pinnate species (Phaeodactylum tricornutum, Haslen ostrearia, Navicula perminuta) [22].…”

Metabolomic Profiling of 13 Diatom Cultures and Their Adaptation to Nitrate-Limited Growth Conditions

“…Hence galactolipids synthesized according to the “eukaryotic” pathway contain predominantly 18-C fatty acid in both sn –1 and sn –2 positions [ 52 ]. Mono- and digalactosyldiacylglycerols from diatoms are mainly synthesised in the “prokaryotic” pathway, as these compounds contain 16-C fatty acids in the sn–2 position [ 53 , 54 ]. Thus, we can deduce the fatty acid chain length in galactolipids presented in this report.…”