Characterization of major lipid droplet proteins from Dunaliella

Abstract

Many green algal species can accumulate large amounts of triacylglycerides (TAG) under nutrient deprivation, making them a potential source for production of biodiesel. TAG are organized in cytoplasmic lipid bodies, which contain a major lipid droplet protein termed MLDP. Green algae MLDP differ in sequence from plant oleosins and from animal perilipins, and their structure and function are not clear. In this study, we describe the isolation of MLDP from three species of the extreme halotolerant green algae Dunaliella. Sequence alignment with other green algae MLDP proteins identified a conserved 4-proline domain that may be considered as a signature domain of Volvocales green algae MLDP. Gold immunolabeling localized MLDP at the surface of lipid droplets in D. salina. The induction of MLDP by nitrogen deprivation is kinetically correlated with TAG accumulation, and inhibition of TAG biosynthesis impairs MLDP accumulation suggesting that MLDP induction is co-regulated with TAG accumulation. These results can lead to a better understanding of the structure and function of Volvocales green algae MLDP proteins.

Major Lipid Body Protein: A Conserved Structural Component of Lipid Body Accumulated during Abiotic Stress in S. quadricauda CASA-CC202

“…D. salina MLDP shares high homology with conserved proline-rich domain in C-terminal end of green algal linage. In addition, MLDP expression also correlated with the high-lipid accumulation (Davidi et al, 2012). Multiple sequence alignment of major oil globule proteins from Dunaliella, C. reinhardtii, and H. pluvialis revealed the consistence of 21 amino acids conserved motif, with four proline residues close to the C-terminal end.…”

“…Multiple sequence alignment of major oil globule proteins from Dunaliella, C. reinhardtii, and H. pluvialis revealed the consistence of 21 amino acids conserved motif, with four proline residues close to the C-terminal end. MLDP of green algae does not show any sequence homology to plant oleosins, to mammalian perilipins, and not even to diatoms or to any other alga whose genome is sequenced, suggesting that MLDPs are unique to the green algal lineage (Davidi et al, 2012).…”

“…MLDP abundance positively correlates with the accumulation of TAGs (Tsai et al, 2014). During nitrogen starvation, both MLDP and TAG were over accumulated, and the inhibition of TAG biosynthesis impairs MLDP level, suggesting that MLDP induction is coregulated with TAG accumulation in Dunaliella (Davidi et al, 2012). Besides MLDP being a major structural protein of LDs proteome, it also contains many regulatory enzymes, such as acyl-activating enzymes, acyl transferase, or lipases, involved in lipid biosynthesis as well as the maturation of LDs (Huang, 1992;Brown, 2001;Athenstaedt and Daum, 2006).…”

“…Like microalgae, plants also store oil in specialized compartments known asLDs, oil bodies/ globules or oleosomes. The neutral storage lipids (mainly TAGs) are stored in these spherical organelles enclosed by a membrane lipid monolayer coated with proteins (Davidi et al, 2012).…”

“…MLDP has been reported in green algal lineages, such as Chlorella vulgaris, Volvox carteri, Dunaliella salina, and Haematococcus pluvialis, however not mapped in diatoms, red algae, or seed plants for which sequenced genomes are available (Moellering and Benning, 2010;Peled et al, 2011;Davidi et al, 2012). D. salina MLDP shares high homology with conserved proline-rich domain in C-terminal end of green algal linage.…”