Involvement of a novel protein kinase C (nPKC) in immunocompetence in hemocytes of white shrimp, Litopenaeus vannamei.

Complementary (c)DNA encoding novel protein kinase C (PKC) messenger (m)RNA of the white shrimp Litopenaeus vannamei, consisted of 2454-bp cDNA containing an open reading frame (ORF) of 2232 bp, belonging to the novel (n)PKC family of proteins characterized by their containing two phorbol ester/diacylglycerol-binding domains (C1 domain), a C2 domain, and a catalytic domain of the serine/threonine kinase, designated LvnPKC. A comparison of amino acid sequences showed that LvnPKC was closely related to arthropod nPKC. LvnPKC cDNA was detected in all tested tissues with a real-time PCR including the hepatopancreas, gills, muscles, subcuticular epithelium, abdominal nerve, thoracic nerve, brain, the stomach, heart, and especially in hemocytes and the intestines. Moreover, significantly upregulated LvnPKC expression was only observed in the eyestalk, brain, and hepatopancreas of shrimp transferred from 28 °C to 18 °C for 30 min. Induction of LvnPKC expression in hemocytes of L. vannamei injected with Vibrio alginolyticus at 105 cfu shrimp-1 was detected earlier than in those injected with 103 cfu shrimp-1. Shrimp received LvnPKC-dsRNA for 1 days specifically depleted the expression of LvnPKC mRNA in hemocytes compared those of diethylpyrocarbonate water treatment. After that, significantly decreased expressions of lipopolysaccharide - and ß-1,3-glucan-binding protein, prophenoloxidase-activating enzyme, peroxinectin, prophenoloxidase I, and prophenoloxidase II in the prophenoloxidase-activating system; lysozyme and cytosolic manganese superoxide dismutase and mitochondrial manganese superoxide dismutase in the antioxidant system were observed. We therefore concluded that LvnPKC is involved in immune defense of L. vannamei exposed to hypothermal stress or infected with V. alginolyticus.

The hot-water extract of leaves of noni, Morinda citrifolia, promotes the immunocompetence of giant freshwater prawn, Macrobrachium rosenbergii.

The hot-water Morinda citrifolia leaf extract (HMLE) was prepared for in vitro assessment on phenoloxidase (PO) activity, respiratory bursts (RBs), and phagocytic activity (PA). Furthermore, the HMLE was administrated in the diet at 0.6, 3, and 6 g (kg diet)-1 for Macrobrachium rosenbergii, and the potential effects on the immunocompetence of prawns were evaluated. PO activity, RBs, and PA in hemocytes incubated with the HMLE at 140, 20, 20, and 140 mg l-1 significantly increased. The immune parameters of the total hemocyte count (THC), differential hemocyte count (DHC), RBs, PO activity, superoxide dismutase (SOD) activity, PA, transglutaminase (TG) activity and hemolymph clotting time were evaluated before and after 1, 3, 5, 7, and 9 weeks of the feeding trial. During 9 weeks of the feeding trial, higher THCs, DHCs, RBs, PO, and TG as well as accelerated clotting times were observed in prawns fed HMLE-containing diets at 0.6 g kg-1. The mRNA expressions of prophenoloxidase, TG, crustin, and lysozyme of prawns fed HMLE-containing diets at 0.6 g kg-1 for 9 weeks of the feeding trial significantly increased. The susceptibility of prawns fed the HMLE at 0.6 g kg-1 to Lactococcus garvieae infection significantly decreased, and the relative survival percentage was 23.1%. We therefore found that HMLE administrated through the diet at 0.6 g kg-1 was capable of enhancing the immunity and resistance against L. garvieae in M. rosenbergii.