Chemistry of oxylipin pathways in marine diatoms

Oxylipins are important signal transduction molecules widely distributed in animals
and plants where they regulate a variety of events associated with physiological and
pathological processes. The family embraces several different metabolites that share a common
origin from the oxygenase-catalyzed oxidation of polyunsaturated fatty acids. The biological
role of these compounds has been especially studied in mammalians and higher
plants, although a varied and very high concentration of these products has also been reported
from marine macroalgae. This article gives a summary of our results concerning the oxylipin
chemistry of marine diatoms, a major class of planktonic microalgae that discourage predation
from their natural grazers, zooplanktonic copepods, using chemical warfare. These apparently
harmless microscopic cells produce a plethora of oxylipins, including short-chain
unsaturated aldehydes, hydroxyl-, keto-, and epoxyhydroxy fatty acid derivatives, that induce
reproductive failure in copepods through abortions, congenital malformations, and reduced
larval growth. The biochemical process involved in the production of these compounds
shows a simple regulation based on decompartmentation and mixing of preexisting enzymes
and requires hydrolysis of chloroplast-derived glycolipids to feed the downstream activities
of C16 and C20 lipoxygenases.