Soy Isoflavones Induce Feminization of Japanese Eel (Anguilla japonica).

Under aquaculture conditions, Japanese eels (Anguilla japonica) produce a high percentage of males. However, females gain higher body weight and have better commercial value than males, and, therefore, a high female ratio is required in eel aquaculture. In this study, we examined the effects of isoflavones, genistein, and daidzein on sex differentiation and sex-specific genes of eels. To investigate the effects of these phytoestrogens on the gonadal sex, we explored the feminizing effects of soy isoflavones, genistein, and daidzein in a dose-dependent manner. The results showed that genistein induced feminization more efficiently than daidzein. To identify the molecular mechanisms of sex-specific genes, we performed a comprehensive expression analysis by quantitative real-time PCR and RNA sequencing. Phenotypic males and females were produced by feeding elvers a normal diet or an estradiol-17ß- or genistein-treated diet for 45 days. The results showed that female-specific genes were up-regulated and male-specific genes were down-regulated in the gonads, suggesting that genistein induces feminization by altering the molecular pathways responsible for eel sex differentiation.

3-ß-Glucosyl-3'-ß-quinovosyl zeaxanthin, a novel carotenoid glycoside synthesized by Escherichia coli cells expressing the Pantoea ananatis carotenoid biosynthesis gene cluster.

Escherichia coli cells that express the full six carotenoid biosynthesis genes (crtE, crtB, crtI, crtY, crtZ, and crtX) of the bacterium Pantoea ananatis have been shown to biosynthesize zeaxanthin 3,3'-ß-D-diglucoside. We found that this recombinant E. coli also produced a novel carotenoid glycoside that contained a rare carbohydrate moiety, quinovose (chinovose; 6-deoxy-D-glucose), which was identified as 3-ß-glucosyl-3'-ß-quinovosyl zeaxanthin by chromatographic and spectroscopic analyses. The chirality of the aglycone of these zeaxanthin glycosides had been shown to be 3R,3'R, in which the hydroxyl groups were formed with the CrtZ enzyme. It was here demonstrated that zeaxanthin synthesized from ß-carotene with CrtR or CYP175A1, the other hydroxylase with similar catalytic function to CrtZ, possessed the same stereochemistry. It was also suggested that the singlet oxygen-quenching activity of zeaxanthin 3,3'-ß-D-diglucoside, which has a chemical structure close to the new carotenoid glycoside, was superior to that of zeaxanthin.