The demand for novel biocatalysts is increasing in modern biotechnology, which greatly stimulates the development of powerful tools to explore the genetic resources in the environment. Metagenomics, a culture independent strategy, provides an access to valuable genetic resources of the uncultured microbes. In this study, two novel esterase genes designated as estA and estB, which encoded 277- and 328-amino-acid peptides, respectively, were isolated from a marine microbial metagenomic library by functional screening, and the corresponding esterases EstA and EstB were biochemically characterized. Amino acid sequence comparison and phylogenetic analysis indicated that EstA together with other putative lipolytic enzymes was closely related to family III, and EstB with its relatives formed a subfamily of family IV. Site-directed mutagenesis showed that EstA contained classical catalytic triad made up of S146-D222-H255, whereas EstB contained an unusual catalytic triad which consisted of S-E-H, an important feature of the subfamily. EstA exhibited habitat-specific characteristics such as its high level of stability in the presence of various divalent cations and at high concentrations of NaCl. EstB displayed remarkable activity against p-nitrophenyl esters and was highly stable in 30% methanol, ethanol, dimethylformamide, and dimethyl sulfoxide, making EstB a potential candidate for industrial applications.

After 480 days of age, high-producing hens are likely to be subject to ovarian aging, mainly due to oxidative stress. In this study, the amelioration of ovarian aging in chickens, using a plant antioxidant, lycopene, was investigated. The activity of the Nrf2/HO-1 pathway in chicken ovaries at different ages (90, 150, 280 and 580 days old) were compared to elucidate any age-related changes. Subsequently, the putative attenuating effect of lycopene (100 ng/mL) on ovarian aging was evaluated through the establishment of a D-gal-induced aging ovarian culture model. The cultured ovarian tissues of young (280 days) and old (580 days) hens were treated with lycopene for 72 h to verify protective effects of lycopene on naturally aged ovaries. Results showed that the Nrf2/HO-1 pathway was down-regulated during the ovarian aging process. Lycopene rescued the decreased antioxidant capacity by increasing the activities of antioxidases and activating the Nrf2/HO-1 pathway in both D-gal-induced and naturally aged ovaries. Moreover, lycopene promoted cell proliferation and inhibited apoptosis in both D-gal-induced and naturally aged ovaries. Lycopene also alleviated D-gal-induced mitochondrial damage in the living granulosa cells. In conclusion, lycopene can effectively ameliorate the oxidative stress in aging hen ovaries via the activation of the Nrf2/HO-1 pathway.

Follicle-stimulating hormone (FSH) and KIT signaling are required for ovarian development. In this study the interactive effect of FSH and stem cell factor (SCF) on folliculogenesis was investigated in the chicken. Correlated changes between the FSH receptor and the expression of KIT signaling genes were seen to be involved in the formation of the chicken primordial follicles. Follicle-stimulating hormone and SCF displayed a reciprocal stimulating effect in the promotion of folliculogenesis involving elevated phosphorylation of mitogen-activated protein kinases (MAPK) and protein kinase B (AKT) proteins. Knockdown of c-KIT or SCF reduced the stimulatory effect of FSH on KIT signaling as well as upon MAPK and AKT phosphorylation. Treatment of FSH and SCF in combination enhanced ovarian cell proliferation and N-cadherin expression, but inhibited cell apoptosis and E-cadherin expression. Overall, the reciprocal stimulating effect of FSH and SCF in promoting chicken follicle assembly involving accelerated ovarian cell proliferation, N-cadherin expression, inhibited cell apoptosis, and E-cadherin expression is demonstrated.

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