The lectin domain containing proteins with mucosal immunity and digestive functions in oyster Crassostrea gigas

Lectins are carbohydrate-binding proteins with lectin domains, which are extensively studied for their numerous roles in biological recognition. However, the lectin domain containing proteins (LDCPs) chimerized with other non-lectin domains have not received sufficient attention. In the present study, a genome-wide survey of LDCPs in oyster Crassostrea gigas was conducted, and an expansive 640 LDCPs derived from ten lectin domains were identified and functionally explored. In these LDCPs, a total of 282 kinds of domains were predicted, and 90% of the LDCPs contained more than one kind of domain. The lectin domains were frequently fused with non-lectin domains, such as epidermal growth factor domain and peptidase related domains, which supplied LDCPs with more diversity in structures and functions. The C-type lectin domains were the most abundant domains in LDCPs, and they were largely co-existed with non-lectin domains of complement activation-related domains (such as CUB domain and PAN-1 domain) but relative independence with other lectin domains. Furthermore, the C-type lectin domain containing proteins (CTLPs) found to mainly act as pattern immune recognition receptors and were highly expressed in mucosal tissues (digestive gland, male gonad and labial palp) to provide mucosal immune protections. The Concanavalin A-like lectin domains were the second richest domains in LDCPs, and they were mostly constructed into chimeric proteins with epidermal growth factor domain and peptidase related domains. The Concanavalin A-like lectin domain containing proteins (CALPs) were significantly enriched with peptidase activities and mainly expressed in digestive tissues. All the results suggested the mucosal immunity and digestive functions of oyster LDCPs, which provided a fresh idea about the functions of invertebrate lectin family.

Impact of essential oils and organic acids on the growth performance, digestive functions and immunity of broiler chickens

The aim of the experiment was to study the effects of feeding blends of sorbic acid, fumaric acid, and thymol (EOA) on growth performance, digestive functions, and immunity of broiler chickens. A total of 640 one-day-old male Cobb 500 chicks with similar BW (41.8 ± 0.6 g) were randomly divided into 4 dietary treatment groups consisting of 10 replicates with 16 birds per replicate and fed a basal diet until d 42 (CON) or diets with 0.15 g/kg enramycin during the grower period (AG), 0.30 g/kg EOA during the grower period (EG), or 0.30 g/kg EOA during the finisher period (EF). At d 42, the feed conversion ratio was reduced (P < 0.05) for birds in EG group compared with other groups. Birds in EG group showed a higher villus height of the duodenum and jejunum and muscular layers of the duodenum and ileum than birds in CON group (P < 0.05). Compared with other groups, crypt depth of the jejunum and ileum was markedly increased (P < 0.05) by EOA supplementation during the finisher period at d 42. The EOA supplementation during grower period increased significantly lipase, trypsin and chymotrypsin activities of the duodenum at d 21 and 42, as well as lipase and trypsin at d 21, and trypsin and chymotrypsin at d 42 in the jejunum, and trypsin and chymotrypsin activities of the ileum at d 21 compared to the control diet (P < 0.05). Birds of EG and EF groups showed a higher (P < 0.05) spleen index than birds of CON group. The level of secretory immunoglobulin A in duodenal and ileal mucosa was increased (P < 0.05) in EF group at d 42 compared with other groups. In conclusion, the results indicate that EOA can be effectively applied in broiler diets, especially during the grower phase by improving intestinal morphology and increasing digestive enzyme activity.