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Liu H.,Shantou University | Liu H.,Mariculture Research Center for Subtropical Shellfish and Algae | Liu H.,Chinese Academy of Sciences | Zhang H.,Shantou University | And 5 more authors.
Journal of Agricultural and Food Chemistry | Year: 2014

Long-chain polyunsaturated fatty acids (LC-PUFAs) are essential in important physiological processes. However, the endogenous PUFA biosynthesis pathway is poorly understood in marine bivalves. Previously, a fatty acyl desaturase (Fad) with Δ5 activity was functionally characterized and an elongase termed Elovl2/5 was reported to efficiently elongate 18:2n-6 and 18:3n-3 to 20:2n-6 and 20:3n-3 respectively in Chlamys nobilis. In this study, another elongase and another Fad were identified. Functional characterization in recombinant yeast showed that the newly cloned elongase can elongate 20:4n-6 and 20:5n-3 to C22 and C24, while the newly cloned scallop Fad exhibited a Δ8-desaturation activity, and could desaturate exogenously added PUFA 20:3n-3 and 20:2n-6 to 20:4n-3 and 20:3n-6 respectively, providing the first compelling evidence that noble scallop could de novo biosynthesize 20:5n-3 and 20:4n-6 from PUFA precursors though the "Δ8 pathway". No Δ6 or Δ4 activity was detected for this Fad. Searching against our scallop transcriptome database failed to find any other Fad-like genes, indicating that noble scallop might have limited ability to biosynthesize 22:6n-3. Interestingly, like previously characterized Elovl2/5, the two newly cloned genes showed less efficient activity toward n-3 PUFA substrates than their homologous n-6 substrates, resulting in a relatively low e fficiency to biosynthesize n-3 PUFA, implying an adaption to marine environment. © 2014 American Chemical Society. Source


Liu H.,Shantou University | Liu H.,Mariculture Research Center for Subtropical Shellfish and Algae | Liu H.,Chinese Academy of Sciences | Zheng H.,Shantou University | And 18 more authors.
BMC Genomics | Year: 2015

Background: The noble scallop Chlamys nobilis Reeve displays polymorphism in shell and muscle colors. Previous research showed that the orange scallops with orange shell and muscle had a significantly higher carotenoid content than the brown ones with brown shell and white muscle. There is currently a need to identify candidate genes associated with carotenoid-based coloration. Results: In the present study, 454 GS-FLX sequencing of noble scallop transcriptome yielded 1,181,060 clean sequence reads, which were assembled into 49,717 isotigs, leaving 110,158 reads as the singletons. Of the 159,875 unique sequences, 11.84% isotigs and 9.35% singletons were annotated. Moreover, 3,844 SSRs and over 120,000 high confidence variants (SNPs and INDELs) were identified. Especially, one class B scavenge receptor termed SRB-like-3 was discovered to express only in orange scallops and absent in brown ones, suggesting a significant association with high carotenoid content. Down-regulation of SRB-like-3 mRNA by RNA interference remarkably decreased blood carotenoid, providing compelling evidence that SRB-like-3 is an ideal candidate gene controlling carotenoid deposition and determining orange coloration. Conclusion: Transcriptome analysis of noble scallop reveals a novel scavenger receptor significantly associated with orange scallop rich in carotenoid content. Our findings pave the way for further functional elucidation of this gene and molecular basis of carotenoid deposition in orange scallop. © 2015 Liu et al. Source


Zheng H.,Shantou University | Zheng H.,Mariculture Research Center for Subtropical Shellfish and Algae | Zhang T.,Shantou University | Zhang T.,Mariculture Research Center for Subtropical Shellfish and Algae | And 6 more authors.
Aquaculture Research | Year: 2013

The noble scallop Chlamys nobilis is polymorphic in its shell colour, which includes orange, orange-purple, purple and brown. In this study, the inheritance of shell colours of this species was investigated by analysing shell colour segregation in juvenile scallops produced from cross-fertilization. Totally, twenty two families derived from four types of parental crosses were produced. The results clearly demonstrated that shell colour in this species was consistently inherited but insensitive to the environmental factors given that each family was maintained in a common environment. The pattern of the four superficial shell colours in C. nobilis appears to be genetically controlled by the interaction of one pair of nonallelic genes, with one locus showing dominance epistasis to the other one. One-locus-three-allele model was proposed to explain the genetic relationship of the orange-purple colour dominant to the purple and brown colours, and the purple colour dominant to the brown colour. While the phenotypic ratio of 12:3:1 detected in one specific family showed that the dominant allele of the other locus controlling orange colour may mask the effect of the locus controlling orange-purple, purple and brown colours. The present results provide a genetic basis for selective breeding in the noble scallop in terms of shell colour. © 2012 John Wiley & Sons Ltd. Source


Zheng H.,Shantou University | Zheng H.,Mariculture Research Center for Subtropical Shellfish and Algae | Liu H.,Shantou University | Liu H.,Mariculture Research Center for Subtropical Shellfish and Algae | And 6 more authors.
Aquaculture | Year: 2012

The noble scallop Chlamys nobilis is an important edible marine bivalve, which has been cultured in the Southern Sea of China since 1980s. Our previous study showed that the total carotenoid content (TCC) in this species was related to body tissue, shell color, and gender, which was the highest in the ovary of the scallops with orange shell and adductor muscle. In the present study, TCC and total lipid content (TLC) in three tissues of adductor muscle, mantle and gonad at different days were determined and compared using four groups of scallops including gonad mature male (MM), gonad mature female (MF), gonad gametocytogenesis male (GcM), and gonad gametocytogenesis female (GcF) and correlations between TCC and TLC for different tissues were analyzed in order to find out how they change during gonad maturation and whether they have correlation with each other in this species. All employed scallops were from the same family produced in autumn 2008 and had the same orange shell, mantle and adductor muscle with higher TCC. The present results showed that both TCC and TLC changed during maturation, but changing trend was different among tissues. In adductor muscle, TCC increased for MM and MF, but decreased for GcM and GcF; TLC had no significant change for all groups. In mantle, TCC significantly changed only in the GcF, which decreased from 327.18μgg -1 to 257.96μgg -1; TLC strikingly changed only in the MF, which increased from 5.33% to 6.77%. In gonad, TCC decreased in MM and increased in other groups; TLC increased in all groups. Particularly interesting and important, a significantly positive correlation (P<0.05) between TCC and TLC was detected in the gonad tissues during maturation, which was also for the first time reported in marine mollusks. The present results also firstly demonstrated that both carotenoid and lipid not only were significantly accumulated in gonad, but also might be transferred from other tissues during maturation in mollusks, particularly in the female. © 2012 Elsevier B.V. Source


Liu H.,Shantou University | Liu H.,Mariculture Research Center for Subtropical Shellfish and Algae | Zheng H.,Shantou University | Zheng H.,Mariculture Research Center for Subtropical Shellfish and Algae | And 9 more authors.
Aquaculture | Year: 2013

Enzymes that lengthen the carbon chain of polyunsaturated fatty acids (PUFAs) are keys to the biosynthesis of the highly unsaturated fatty acids. Here we report on the molecular cloning and functional characterization of a cDNA encoding a putative elongase of very long-chain fatty acids (ELOVL), a critical enzyme that catalyses the elongation of fatty acids (FAs) including PUFAs. The full length cDNA of the fatty acyl elongase from the noble scallop Chlamys nobilis was isolated by Rapid Amplification of cDNA Ends (RACE). The amplified cDNAs encoded a putative open reading frame (ORF) of 307 amino acids that contained histidine box HXXHH motif conserved in all elongases. Phylogenetic analysis suggested that the putative elongase was placed in the same group with ELOVL2 and ELOVL5, which had been demonstrated to be critical enzymes participating in the biosynthesis of PUFAs in vertebrates. Heterologous expression in yeast Saccharomyces cerevisiae demonstrated that the ORF encoded an elongase with the ability to lengthen n. -. 3 and n. -. 6 PUFA substrates with chain lengths of C18 and C20, exhibiting similar substrate specificities to vertebrate ELOVL5. Moreover, the noble scallop elongase could lengthen monounsaturated fatty acids to low activity, but not saturated fatty acids. The interesting point was that this elongase converted n. -. 6 PUFA substrates more efficiently than their homologous n. -. 3 substrates, suggesting that n. -. 6 PUFAs might have particular biological significance in C. nobilis. © 2013 Elsevier B.V. Source

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