Characterization of transforming growth factor beta regulator 1-like and association between its expression levels and growth of the giant tiger shrimp Penaeus monodon

Structural and functional analysis of transforming growth factor beta regulator 1 (TBRG1) in the red swamp crayfish Procambarus clarkii: The initial insight into TBRG1's role in invertebrate immunity

The transforming growth factor beta regulator 1 (TBRG1) is a growth inhibitory protein that acts as a tumor suppressor in human cancers, gaining its name for the transcriptional regulation by TGF-β. While extensive research has been conducted on the tumor-related function of TBRG1 in mammals, its significance in invertebrates remains largely unexplored. In this study, a homolog of TBRG1 was first structurally and functionally analyzed in the red swamp crayfish Procambarus clarkii. The full-length cDNA sequence was 2143 base pairs (bp) with a 1305 bp open reading frame (ORF) encoding a deduced protein of 434 amino acids (aa). The changes of PcTBRG1 transcripts upon immune challenges indicated its involvement in innate immunity. After knocking down PcTBRG1, the decline of bacteria clearance capacity revealed the participation of PcTBRG1 in the immune response. Furthermore, the downregulation of AMPs' expression after the cotreatment of RNAi and bacteria challenge suggested that PcTBRG1 might participate in innate immunity through regulating AMPs' expression. These results provided initial insight into the immune-related function of TBRG1 in invertebrates.

Transcriptome comparison for identification of pigmentation-related genes in different color varieties of Siamese fighting fish Betta splendens

Transcriptome comparison was performed to identify genes expressed in skin, muscle and tails of mono-color (Red, Blue, Black, White and Yellow), bi-color (Cambodian) and multi-color (Marble) varieties of Siamese fighting fish Betta splendens. In total, 163,140 unigenes covering 26.348 Gb were found. Of these, 93,899 (57.55 %) unigenes significantly matched at least one database. In total, 5039 differentially expressed genes (DEGs) were found where 2415 genes (47.93 %) showed higher expression and 2624 genes (52.07 %) showed lower expression for all pairwise comparisons. DEGs between paired color varieties were 133-443. Of these, 38-220 genes were more highly expressed while 37-280 genes were more lowly expressed relative to the compared varieties. A total of 897 sequences (148 genes) significantly matched pigmentation-related genes of Danio rerio (E-value < 1e-06). Of these, 19 DEGs were identified. Examples are tyrosinase-related protein 1a (BsTyrp1a), epidermal growth factor receptor (BsEgfr) and neurofibronin 1a (BsNf1a). Moreover, 711,123 SNPs were identified and 1365 of these were located in pigmentation-related genes. Interestingly, an A > C₄₇₄ SNP in the gene BsTrpm7 and an indel (position 3571) in the BsItgb1a gene were found only in Cambodian. A C > T₂₅₂₀ SNP in BsFzd4 and 10 of 11 SNPs in BsTyrp1a were found only in Black. Different expression levels (P < 0.05) were found for tyrosinase (BsTyr), BsTyrp1a, BsNf1a and BsEgf1 among skin, body muscle and tails of the same variety and among the same tissues of different varieties (Red, Green, Blue, Black, Cambodian and Multi-colors, N = 5 each).

A potential negative regulation of myostatin in muscle growth during the intermolt stage in Exopalaemon carinicauda

Muscle growth in crustacean is a complicated process where the muscle grows and develops through muscle restoration, and the growth rate depends on the net muscle gain during molting. Myostatin (MSTN) is a conserved inhibitor of muscle growth in vertebrates, but until now solid evidence supporting a similar function of MSTN in invertebrates has been lacking. In this study, we identified and characterized MSTN from the shrimp Exopalaemon carinicauda (EcMSTN) to better understand its biological function. The full-length cDNA of EcMSTN was 1,518 bp, encoding 428 amino acid residues, and the genomic sequence was 1,851 bp, including three exons and two introns. EcMSTN was expressed in a wide range of tissues, but predominantly detected in the abdominal muscle (P < 0.05). Low expression was detected in the cleavage, blastula and gastrula stages in the early development stages, increasing after the nauplius stage. EcMSTN expression was negatively correlated with the growth traits. After EcMSTN knockdown using RNA interference, EcMSTN expression was down-regulated in the abdominal muscle and up-regulated the expression of growth-related genes, including fast myosin heavy chain and skeletal muscle actin 3. After inhibiting EcMSTN for 5 weeks, the RNAi-treated shrimp with reduced EcMSTN levels exhibited a dramatically higher body weight compared with that of the control group. Association analysis revealed that two SNP loci g.Mstn220 and g.Mstn567 were markedly associated with both body weight and body length. The results would clarify the negative role of EcMSTN in regulating muscle growth during the intermolt stage and provide growth-related markers for molecular marker assisted breeding of E. carinicauda.

A SNP of the hemocyanin gene (LvHc) is a marker for high growth and ammonia-tolerance in Pacific white shrimp Litopenaeus vannamei

Expression levels of hemocyanin (LvHc), activating transcription factor 4 (LvAtf4), glutathione S-transferase (LvGst), caspase 2 (LvCasp2) and anti-lipopolysaccharide factor (LvAlf) were examined in the hepatopancreas of Pacific white shrimp Litopenaeus vannamei juveniles exposed to a lethal concentration of ammonia-N (32.15 mg/l). The expression levels of all transcripts except LvAlf were significantly greater (P < 0.05) in tolerant shrimp (Lv-AT; N = 30) that survived up to 72 h post treatment (hpt) than in susceptible shrimp (Lv-AS24 and Lv-AS72; N = 45 and 15), that died within 24 h or between 24 and 72 hpt, respectively. Subsequently, effects of non-lethal concentrations of ammonia-N (control, 10 and 20 mg/l) on the expression of LvHc in juvenile shrimp were examined. Compared to the control, expression levels of LvHc transcripts in hemocytes and the hepatopancreas of tested shrimp changed after exposure to ammonia-N. One SNP (C > T₅₄₅) was found in the LvHc₃₂₂ gene segment. Real-time PCR amplification of specific alleles (real-time PASA) was developed for detection of C > T₅₄₅ genotypes. Juveniles in the lethal exposure test that carried a C/T₅₄₅ genotype showed a greater average body weight and total length (8.46 ± 0.36 g and 10.05 ± 0.16 cm) than those with a C/C₅₄₅ genotype (7.48 ± 0.31 g and 9.60 ± 0.13 cm) (P < 0.05). Similar results were found in the second generation (G2) of a growth-improved stock (3 and 4 families of BIOTEC-G2-L1 and BIOTEC-G2-L2) and in commercially farmed shrimp (2 groups). Accordingly, expression levels and SNP of LvHc can serve as markers for selection high growth performance in ammonia-tolerant L. vannamei.

Molecular characteristic of activin receptor IIB and its functions in growth and nutrient regulation in Eriocheir sinensis

Activin receptor IIB (ActRIIB) is a serine/threonine-kinase receptor binding with transforming growth factor-β (TGF-β) superfamily ligands to participate in the regulation of muscle mass in vertebrates. However, its structure and function in crustaceans remain unknown. In this study, the ActRIIB gene in Eriocheir sinensis (Es-ActRIIB) was cloned and obtained with a 1,683 bp open reading frame, which contains the characteristic domains of TGF-β type II receptor superfamily, encoding 560 amino acids. The mRNA expression of Es-ActRIIB was the highest in hepatopancreas and the lowest in muscle at each molting stage. After injection of Es-ActRIIB double-stranded RNA during one molting cycle, the RNA interference (RNAi) group showed higher weight gain rate, higher specific growth rate, and lower hepatopancreas index compared with the control group. Meanwhile, the RNAi group displayed a significantly increased content of hydrolytic amino acid in both hepatopancreas and muscle. The RNAi group also displayed slightly higher contents of saturated fatty acid and monounsaturated fatty acid but significantly decreased levels of polyunsaturated fatty acid compared with the control group. After RNAi on Es-ActRIIB, the mRNA expressions of five ActRIIB signaling pathway genes showed that ActRI and forkhead box O (FoxO) were downregulated in hepatopancreas and muscle, but no significant expression differences were found in small mother against decapentaplegic (SMAD) 3, SMAD4 and mammalian target of rapamycin. The mRNA expression s of three lipid metabolism-related genes (carnitine palmitoyltransferase 1β (CPT1β), fatty acid synthase, and fatty acid elongation) were significantly downregulated in both hepatopancreas and muscle with the exception of CPT1β in muscles. These results indicate that ActRIIB is a functionally conservative negative regulator in growth mass, and protein and lipid metabolism could be affected by inhibiting ActRIIB signaling in crustacean.

Identification of a Growth-Associated Single Nucleotide Polymorphism (SNP) in Cyclin C of the Giant Tiger Shrimp Penaeus monodon

The full-length cDNA of cyclin C of the giant tiger shrimp Penaeus monodon (PmCyC) was isolated by RACE-PCR. It was 1443 bp in length containing an open reading frame (ORF) of 804 bp and 267 deduced amino acids. Tissue distribution analysis indicated that PmCyC was more abundantly expressed in ovaries and testes than other tissues of female and male juveniles (P < 0.05). A pair of primers was designed, and an amplification product of 403 bp containing an intron of 123 bp was obtained. Polymorphism of amplified PmCyC gene segments of the 5th (3-month-old G5, N = 30) and 7th (5-month-old G7, N = 18) generations of domesticated juveniles was analyzed. Four conserved SNPs (T>C₁₃₄, T>C₁₈₈, G>A₃₇₉, and T>C₃₈₂) were found within the examined sequences. A TaqMan genotyping assay was developed for detection of a T>C₁₃₄ SNP. Association analysis indicated that this SNP displayed significant association with body weight (P < 4.2e-10) and total length (P < 2e-09) of the examined G7 P. monodon (N = 419) with an allele substitution effect of 5.02 ± 0.78 g and 1.41 ± 0.19 cm, respectively. Juveniles with C/C₁₃₄ (22.80 ± 2.51 g and 12.97 ± 0.53 cm, N = 19) and T/C₁₃₄ (20.41 ± 0.93 g and 12.77 ± 0.21 cm, N = 129) genotypes exhibited a significantly greater average body weight and total length than those with a T/T₁₃₄ genotype (14.72 ± 0.53 g and 11.37 ± 0.13 cm, N = 271) (P < 0.05).