Dietary polyunsaturated fatty acids (PUFAs) are critical to the success of ovarian development in marine crustaceans, especially for domesticated species such as the black tiger shrimp Penaeus monodon. These fatty acids are stored in a midgut gland called the hepatopancreas and subsequently serve as an energy source or are incorporated in yolk during ovarian development. PUFAs are known precursors of hydroxy fatty acids, including hydroxyeicosatetraenoic acid and hydroxyeicosapentaenoic acid (HEPE), which are catalyzed by lipoxygenases (LOX). In previous studies, 8-HEPE has been shown to regulate female reproduction and adipogenesis in marine crustaceans. However, whether the biosynthesis of 8-HEPE in these species is the result of LOX activity has yet to be investigated. In this study, 8-HEPE was identified exclusively in P. monodon hepatopancreases using liquid chromatography-mass spectrometry. Treatment with nordihydroguaiaretic acid resulted in the reduction of 8-HEPE, suggesting the enzyme-dependent catalysis of 8-HEPE in hepatopancreases. Additionally, a full-length P. monodon LOX (PmLOX) was amplified from shrimp ovary cDNA. Sequence analysis revealed that the putative PmLOX contains domains and catalytic residues required for LOX catalytic function. Furthermore, PmLOX expression increased steadily as shrimp ovary maturation progressed, while PmLOX expression and the amount of 8-HEPE decreased in shrimp hepatopancreases. These findings not only suggest differential requirements for hydroxy fatty acid biosynthesis in shrimp ovaries and hepatopancreases during the P. monodon ovarian development, but also provide insights into the LOX pathway in marine crustaceans.
