Cloning of the Bovine β-Carotene-15,15’-Oxygenase and Expression in Gonadal Tissues

Abstract

β-carotene-15,15’-oxygenase (βCO), found mainly in intestinal mucosa and liver, is the enzyme responsible for cleaving β-carotene into retinal, which can be used or stored at these sites or carried by the bloodstream to different target cells within the body. We isolated the cDNA for bovine βCO and demonstrated its expression in gonadal tissues. A cDNA of 2130 base pairs (bp) was obtained by reverse transcriptase-polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends (RACE), using degenerate oligonucleotides; the deduced protein shared an identity of 75% with its homologues from other mammalian species. In order to evaluate the expression of this enzyme, we performed RT-PCR and in situ hybridizations in the ovary and testis of bovines. RT-PCR showed the expression of βCO in testis, ovary, and cultured granulosa cells. In situ hybridization of complete ovary and testis revealed expression in granulosa cells and the corpus luteum in the ovary and in germinal and interstitial cells in the testis. These results suggest that beta-carotene could act as a local source of retinoids, which have been shown to be important during proliferation, differentiation, and maturation of both female and male germinal cells.