Physiological role of neutral lipid accumulation in eukaryotic microalgae under stresses

Abstract

In the studies of lipid metabolism of unicellular photoautotrophic eukaryotes (microalgae), the main attention is commonly paid to polar membrane lipids and their fatty acid (FA) composition, whereas neutral lipids, represented predominantly by triacylglycerols (TAG), are insufficiently studied. As was reported recently, the role of these compounds in microalgae is not limited to their storage function. It was found that TAG are frequently involved in adaptation to environmental conditions. This review summarizes experimental data obtained so far allowing to distinguish at least three aspects of TAG adaptive function in microalgae. First, these compounds are the source of long-chain FA, the building blocks for membranes necessary for rearrangements of the photosynthetic apparatus. Second, TAG biosynthesis consumes excessive photoassimilates preventing photooxidative injuries under stresses which reduce cell capacity of photosynthesis product utilization. Third, TAG deposited as cytoplasmic oil bodies form a depot for secondary carotenoids in carotenogenic microalgae producing an optical screen protecting the cell against photodamage by excessive PAR.