Search

As one of the sources of biodiesel, microalgae are expected to solve petroleum shortage. In this study, different concentrations of piperonyl butoxide were added to the culture medium to investigate their effects on the growth, pigment content, lipid accumulation, and content of carotenoids in

Geranylgeranyl diphosphate synthase (GGPS) catalyzes the biosynthesis of geranylgeranyl diphosphate, a key precursor for carotenoid biosynthesis. In this study, a full-length cDNA encoding GGPS from Dunaliella bardawil (DbGGPS) was isolated by rapid amplification of cDNA ends (RACE) for the first time. The full-length cDNA of DbGGPS was 1814 bp, containing a 1074 bp ORF encoding 357 amino acids with a calculated mass of 38.88 kDa. Analysis of DbGGPS genomic DNA revealed that it contained 10 exons and 9 introns. It was predicted that DbGGPS possessed a 48 amino acid transit peptide at its N terminus. Bioinformatic analysis revealed that DbGGPS was a member of a group of polyprenyltransferases with five conserved domains and two highly conserved aspartate-rich motifs. Using heterologous expression, carotenoid complementation assay, and gene deletion analysis, it was shown that the coding region of DbGGPS encodes a functional GGPS. This provides new gene sources for carotenoid genetic engineering.

Dunaliella tertiolecta, a halotolerant alga, can accumulate large amounts of neutral lipid, which makes it a potential biodiesel feedstock. In this study, neutral lipids of D. tertiolecta induced by different salinities or N or P starvation were analyzed by thin-layer chromatography (TLC), flow cytometry (FCM), and confocal laser scanning microscopy (CLSM). High salinities or N or P starvation resulted in a decrease in cell growth and chlorophyll contents of D. tertiolecta. Neutral lipid contents increased markedly after 3-7 days of N starvation or at low NaCl concentrations (0.5-2.0 M). N starvation had a more dramatic effect on the neutral lipid contents of D. tertiolecta than P starvation. Four putative ME isozymes in different conditions can be detected by using isozyme electrophoresis. Two alternative acetyl-CoA producers, ACL and ACS genes, were up-regulated under low salinities and N starvation. It was suggested that low salinities and N starvation are considered efficient ways to stimulate lipid accumulation in D. tertiolecta.