An Evolutionary Perspective on Linoleic Acid Synthesis in Animals.

Area of Science:

• Biochemistry and Evolutionary Biology
• Nutritional Science
• Molecular Biology

Background:

• Dietary nutrients are crucial for organismal growth and development, but the ability to synthesize essential nutrients varies across species.
• Linoleic acid (LA), an unsaturated fatty acid vital for cell physiology, immunity, and reproduction, is considered an essential nutrient for many organisms.
• While plants and microbes synthesize LA, animals were long believed to be incapable of de novo synthesis, necessitating dietary intake.

Purpose of the Study:

• To investigate the mechanisms of linoleic acid (LA) synthesis and its biological functions across different organisms.
• To address why LA synthesis capability has been lost and re-evolved multiple times during invertebrate evolution.
• To identify factors promoting LA synthesis within a phylogenetic context.

Main Methods:

• Literature review of studies on LA synthesis mechanisms and functions.
• Compilation of data on LA synthesis across various organisms.
• Phylogenetic analysis to correlate LA synthesis with evolutionary history.

Main Results:

• Evidence shows active LA synthesis in various animal groups, including insects, nematodes, and pulmonates, challenging previous assumptions.
• The review did not find a clear link between proposed hypotheses and the presence or absence of LA synthesis.
• LA synthesis appears to be facilitated by the bifunctionality of desaturase enzymes or driven by a combination of selective pressures.

Conclusions:

• The ability to synthesize linoleic acid (LA) is not universally absent in animals and has evolved independently in different invertebrate lineages.
• The evolutionary gain and loss of LA synthesis are complex, potentially involving enzyme bifunctionality and diverse selective pressures.
• Further research is needed to fully elucidate the evolutionary drivers and molecular mechanisms underlying LA synthesis variability.