Transcriptome analysis provides insights into the high ability to synthesize fatty acids in "yellow oil" mud crab (Scylla paramamosain).

Yellow oil mud crab (YOC) is a new variant of mud crab (Scylla paramamosain), which was attracted much attention in recent years due to its high level of nutrition. However, the nutritive values and the physiological changes in YOC have not been clearly understood. In this study, we aimed to identify the nutrient compositions (including total carotenoid content (TCC), total lipid content (TLC), total antioxidant capacity (TAC), and fatty acids) and differences in genes related to the biosynthesis of fatty acids using transcriptome analysis in YOC in comparison with those of normal mud crabs. As a result, observations on the morphological characteristics showed that the YOC exhibits a difference in the color of the muscle, gills (orange-yellow), and hemolymph (yellow) compared with the normal female crabs (NFC) (blue or nattier blue). The TCC and TLC (84.96 ± 9.65 µg/g in muscle and 1.39 ± 0.10 µg/mL in hemolymph) or TAC (1.52 ± 0.17 mM in hemolymph) of YOC were higher than that of NFC and normal male crab (NMC). YOC had lower saturated fatty acids, but higher unsaturated fatty acids, as well as the ratio of n-3/n-6 of fatty acids in muscle and hemolymph, compared with those of NFC and NMC. Furthermore, the transcriptome profile revealed that the unigenes in YOC were enriched in the synthesis of n-3 fatty acids. Furthermore, more unigenes related to 'Biosynthesis of unsaturated fatty acids' were identified in muscle and hemocytes, while fewer were in the gonads of YOC. Additionally, the positive (in muscle and hemocytes) and a negative correlation (in gonads) between expressions of unigenes and contents of TLC, TCC, and UFA were found, indicating a better synthesis ability of fatty acids in the muscle and hemocytes of YOC. Overall, compared to NFC and NMC, YOC has higher nutrients and is a better food nutrient source for humans.

Tuning of strong nonlinearity in radio-frequency superconducting-quantum-interference-device meta-atoms.

Strong nonlinearity of a self-resonant radio-frequency (rf) superconducting-quantum-interference-device (SQUID) meta-atom is explored via intermodulation (IM) measurements. Previous work in zero dc magnetic flux showed a sharp onset of IM response as the frequency sweeps through the resonance. A second onset at higher frequency was also observed, creating a prominent gap in the IM response. By extending those measurements to nonzero dc flux, different dynamics are revealed, including dc flux tunability of the aforementioned gaps and enhanced IM response near geometric resonance of the rf SQUID. These features observed experimentally are understood and analyzed theoretically through a combination of a steady-state analytical modeling and a full numerical treatment of the rf SQUID dynamics. The latter in addition predicts the presence of chaos in narrow parameter regimes. The understanding of intermodulation in rf SQUID metamaterials is important for producing low-noise amplification of microwave signals and tunable filters.

SpTGase plays an important role in the hemolymph clotting in mud crab (Scylla paramamosain).

Transglutaminase (TGase) is important in blood coagulation, a conserved immunological defense mechanism among invertebrates. This study is the first report of the TGase in mud crab (Scylla paramamosain) (SpTGase) with a 2304 bp ORF encoding 767 amino acids (molecular weight 85.88 kDa). SpTGase is acidic, hydrophilic, stable and thermostable, containing three transglutaminase domains, one TGase/protease-like homolog domain (TGc), one integrin-binding motif (Arg270, Gly271, Asp272) and three catalytic sites (Cys333, His401, Asp424) within the TGc. Neither a signal peptide nor a transmembrane domain was found, and the random coil is dominant in the secondary structure of SpTGase. Phylogenetic analysis revealed a close relation between SpTGase to its homolog EsTGase 1 from Chinese mitten crab (Eriocheir sinensis). Expression of SpTGase was investigated using qRT-PCR (1) in eight tissues from healthy mud crabs, with the highest expression in hemocytes, and (2) in response to various immune challenges (Vibrio parahaemolyticus, lipopolysaccharide (LPS) or Poly I:C infection), revealing a major up-regulation in hemocytes, skin, and hepatopancreas during the 96-h post injection. The recombinant SpTGase showed a capacity of agglutination activities on both Gram-negative bacteria and yeast. SpTGase was found to directly interact with another important blood coagulation component clip domain serine protease (SpcSP). Moreover, knockdown of SpTGase resulted in a decreased expression of both clotting protein precursor (SppreCP) and SpcSP and an increase of duration time in the blood coagulation. Taken together, the findings of this study suggest SpTGase play an important role in the hemolymph clotting in mud crab S. paramamosain.

A clip domain serine protease regulates the expression of proPO and hemolymph clotting in mud crab, Scylla paramamosain.

The clip domain serine proteinases (clip-SPs) play vital roles in embryonic development and in various innate immune functions in invertebrates such as antimicrobial activity, cell adhesion, hemolymph clotting, pattern recognition and regulation of the prophenoloxidase system. However, little is known about the role of the clip domain serine proteinase in Scylla paramamosain (designated SpcSP) immunity. In the present study, we cloned a clip-SP from S. paramamosain hemocytes using rapid amplification of cDNA end (RACE) approach. The full-length cDNA of SpcSP was 1823 bp, containing a 5' untranslated region (UTR) of 334 bp, an open reading frame of 1122 bp, and a 3' UTR of 367 bp. The open reading frame encoded a polypeptide of 373 amino acids with a calculated molecular weight of 39.7 kDa and an isoelectric point of 6.64. Structurally, SpcSP has a predicted 21-residue signal peptide and possessed the characteristic features of the clip domain family of serine proteases, namely one clip domain in the amino-terminal with six highly conserved cysteine residues and one enzyme active serine proteinase domain in the carboxyl-terminal with a highly conserved catalytic triad (His156, Asp226, Ser321). Phylogenetic analysis showed that SpcSP was clustered together with PtcSP (clip domain serine proteinase from Portunus trituberculatus). Quantitative real-time PCR (qPCR) analysis showed that the mRNA of SpcSP was constitutively expressed at different levels in all tested tissues in untreated S. paramamosain, with hemocytes and skin expressing the most. The transcriptional level of SpcSP in hemocytes was significantly up-regulated upon challenge with V. parahaemolyticus and LPS, indicating its involvement in antibacterial immune response. Indirect immunofluorescence analysis showed that SpcSP was expressed in the cytoplasm of all three hemocyte cell types (hyaline, semigranular and granular cells). Further, recombinant SpcSP protein exhibited strong binding ability and has antimicrobial activity against both Gram-positive and Gram-negative bacteria as well as fungi. Moreover, knockdown of SpcSP resulted in increased hemolymph clotting time and decreased the mRNA expression of SpproPO mRNA in hemocytes. These findings therefore suggest that SpcSP plays an important role in the antimicrobial defense mechanism of S. paramamosain by regulating the expression of SpproPO and hemolymph clotting in S. paramamosain.

Coherent oscillations of driven rf SQUID metamaterials.

Through experiments and numerical simulations we explore the behavior of rf SQUID (radio frequency superconducting quantum interference device) metamaterials, which show extreme tunability and nonlinearity. The emergent electromagnetic properties of this metamaterial are sensitive to the degree of coherent response of the driven interacting SQUIDs. Coherence suffers in the presence of disorder, which is experimentally found to be mainly due to a dc flux gradient. We demonstrate methods to recover the coherence, specifically by varying the coupling between the SQUID meta-atoms and increasing the temperature or the amplitude of the applied rf flux.