Effects of Mn2+ on neutral lipid content, C4 pathway, and related gene expression in Phaeodactylum tricornutum.

The neutral lipids from the diatom Phaeodactylum tricornutum are a valuable substance with a vital role in biofuel. Increasing the neutral lipid content of P. tricornutum through nutritional stress, such as nitrogen stress or genetic engineering, is often accompanied by reduced growth, which limits the development of microalgae-derived biofuels. Manganese is an essential trace element for plant growth and plays a key role in the light reactions of photosynthesis. This study aimed to determine whether Mn2+ can increase the neutral lipid content. We investigated the effects of Mn2+ on growth, neutral lipid content, photosynthetic pigment content, and fatty acid and photosynthesis-related gene expression and enzyme abundance in P. tricornutum. The algae were exposed to different concentrations of Mn2+ and monitored for growth and neutral lipid and photosynthetic pigment contents. After 7 days of culture, neutral lipid levels were markedly increased in algae exposed to 500 μg·L-1 Mn2+ (1.44 times higher than the control group without Mn2+). To confirm the molecular mechanism of this effect in P. tricornutum treated with Mn2+, the expression of key genes in the fatty acid synthesis pathway (ACC1, LACS1, AGPAT, MCAT) and C4 pathway (ME1, PEPCK1, PEPC, PPDK, CA) were determined by real-time polymerase chain reaction. The expression of genes involved in these pathways reached their peak at a concentration of 500 μg·L-1 Mn2+, consistent with the change in neutral lipid content. Based on these results, we concluded that the neutral lipid content in P. tricornutum was enhanced by Mn2+, likely as a result of increased production of enzymes in the C4 pathway. [ABSTRACT FROM AUTHOR]