A Novel Candidate Gene Associated With Body Weight in the Pacific White Shrimp Litopenaeus vannamei

Structure and function analyses of the SRC gene in Pacific white shrimp Litopenaeus vannamei

SRC gene encodes scavenger receptor class C, a member of the scavenger receptor family, and has only been identified and investigated in invertebrates. Our previous studies have revealed that SRC is a novel candidate gene associated with body weight in Pacific white shrimp (Litopenaeus vannamei). In order to comprehend the underlying mechanism by which LvSRC affects shrimp growth, we analyzed the structure, phylogeny, expression profiles and RNA interference (RNAi) of this gene in L. vannamei. We found that LvSRC contains two CCP domains and one MAM domain, with the highest expression level in the heart and relatively low expression level in other tissues. Notably, LvSRC exhibited significantly higher expression levels in the fast-growing group among groups with different growth rates, suggesting its potential involvement as a gene contributing to the growth of L. vannamei. RNAi of LvSRC inhibited body length and body weight gain compared to the control groups. Moreover, through RNA-seq analysis, we identified 598 differentially expressed genes (DEGs), including genes associated with growth, immunity, protein processing and modification, signal transduction, lipid synthesis and metabolism. Furthermore, Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses revealed significant changes in the signaling pathways related to growth, lipid metabolism and immune response, suggesting that LvSRC exhibits the potential to participate in diverse physiological processes and immune regulation. These findings deepen our understanding of the structure and function of the SRC in shrimp and lay the foundation for further research into the regulatory mechanism of LvSRC. Additionally, they provide potential applications in shrimp genetics and breeding.

Structure and function analyses of the Mmd2 gene in pacific white shrimp Litopenaeus vannamei

Monocyte to macrophage differentiation factor 2 gene (Mmd2) encodes a member of the progestin and adipoQ receptor (PAQR) family, and plays a key role in growth and development. Our previous studies had found Mmd2 (Monocyte to macrophage differentiation factor 2) is a new candidate gene for growth traits in Pacific white shrimp (Litopenaeus vannamei). For the purpose of understanding the underlying mechanism of LvMmd2 affecting the growth of shrimp, we analyzed the gene structure, phylogeny, expression profiles and RNA interference of this gene in L. vannamei. We found the LvMmd2 gene sequence was highly conserved in transmembrane regions, it was widely expressed in different tissues, with the highest expression level in the eye stalk. Knockdown LvMmd2 could significantly promote body length and body weight gain, suggesting it is a growth suppressor. Through transcriptome analysis we identified 422 differentially expressed genes (DEGs) between the dsMmd2 group and control group, among which 337 genes were upregulated in the dsMmd2 group, including numerous muscle-related genes and protein synthesis genes. Further bioinformatics analysis showed that growth, metabolism, and immune-related signal pathway had changed significantly. The above results greatly increase our understanding on the conservative structure and function of LvMmd2 gene, and provide potential application prospects in genetics and breeding.

Genome-wide association study identified genes associated with ammonia nitrogen tolerance in Litopenaeus vannamei

Ammonia nitrogen tolerance is an economically important trait of the farmed penaeid shrimp Litopenaeus vannamei. To identify the genes associated with ammonia nitrogen tolerance, we performed an extreme phenotype genome-wide association study method (XP-GWAS) on a population of 200 individuals. The single nucleotide polymorphism (SNP) genotyping array method was used to construct the libraries and 36,048 SNPs were genotyped. Using the MLM, FarmCPU and Blink models, six different SNPs, located on SEQ3, SEQ4, SEQ5, SEQ7 and SEQ8, were determined to be significantly associated with ammonia nitrogen tolerance. By integrating the results of the GWAS and the biological functions of the genes, seven candidate genes (PDI, OZF, UPF2, VPS16, TMEM19, MYCBP2, and HOX7) were found to be associated with ammonia nitrogen tolerance in L. vannamei. These genes are involved in cell transcription, cell division, metabolism, and immunity, providing the basis for further study of the genetic mechanisms of ammonia nitrogen tolerance in L. vannamei. Further candidate gene association analysis in the offspring population revealed that the SNPs in the genes zinc finger protein OZF-like (OZF) and homeobox protein Hox-B7-like (HOX7) were significantly associated with ammonia nitrogen tolerance trait of L. vannamei. Our results provide fundamental genetic information that will be useful for further investigation of the molecular mechanisms of ammonia nitrogen tolerance. These associated SNPs may also be promising candidates for improving ammonia nitrogen tolerance in L. vannamei.

ATP synthase subunit e is a shrimp growth-associated breeding marker

Penaeus vannamei is one of the most popular aquaculture species in the world. This species is featured with its fast-growing and delicious taste, which drives people develop various strains. During this process identification of trait-associated markers could effectively increase breeding efficiency. Driven by this, we tried to screen fast-growing key regulators via a FACS-based high throughput method, in which 2-NBDG was applied as a fluorescent indicator for direct glucose uptake measurement. Totally six candidate genes were screened out followed by in vitro validation in 293T cells. After that, the correlation between these genes and shrimp growing was further verified in a hybrid lineage. The expression level of two genes including ATP synthase subunit e and inhibitor of apoptosis protein showed some correlation with shrimp growth speed. Furthermore, we tested these two candidate markers in various lineages and confirmed that ATP synthase subunit e could be a shrimp growth-associated breeding marker.

Identification of Growth-Associated Genes by Genome-Wide Association Study and Their Potential Application in the Breeding of Pacific White Shrimp (Litopenaeus vannamei)

The Pacific white shrimp (Litopenaeus vannamei) is the most widely cultured shrimp in the world. A great attention has been paid to improve its body weight (BW) at harvest through genetic selection for decades. Genome-wide association study (GWAS) is a tool to dissect the genetic basis of the traits. In this study, a GWAS approach was conducted to find genes related to BW through genotyping 94,113 single nucleotide polymorphisms (SNPs) in 200 individuals from a breeding population. Four BW-related SNPs located in LG19 and LG39 were identified. Through further candidate gene association analysis, the SNPs in two candidate genes, deoxycytidylate deaminase and non-receptor protein tyrosine kinase, were found to be related with the body weight of the shrimp. Marker-assisted best linear unbiased prediction (MA-BLUP) based on the SNPs in these two genes was used to estimate the breeding values, and the result showed that the highest prediction accuracy of MA-BLUP was increased by 9.4% than traditional BLUP. These results will provide useful information for the marker-assisted breeding in L. vannamei.

Single nucleotide polymorphism associated with disease resistance in Penaeus vannamei

Despite the considerable number of genetic markers published for Penaeus vannamei, the classification of these markers and their standardization in specific databases is still insufficient. As a consequence, access to these markers is difficult, hampering their application in genetic association studies. In this study, all previously described single nucleotide polymorphisms (SNPs) related to resistance for P. vannamei were revised, and 512 SNPs were identified and classified in detail. We observed that most of the SNPs occurred in the proteins including Toll like receptors 1 and 3, hemocyanin large and small subunits, and anti-lipopolysaccharide factors 1 and 2, allowing to propose to use them as targets in association studies involving resistance in P. vannamei. Additionally, the potential effects of the most frequent non-synonymous coding SNPs in the secondary structure of the main target proteins were evaluated using an in silico approach. These data can serve as the starting point for the development of new genetic and computational tools as well as for the design of new association studies that involve resistance in P. vannamei.

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).

The Polymorphism of LvMMD2 and Its Association with Growth Traits in Litopenaeus vannamei

The Pacific white shrimp Litopenaeus vannamei is one of the major economic aquaculture species. The growth trait is considered as the most important trait in L. vannamei aquaculture. Identification of the genetic components underlying growth-related traits in L. vannamei could be useful for the selective breeding of growth trait. Our previous work identified several growth-related SNPs by genome-wide association study (GWAS). Based on the assembled genome, we identified a new candidate gene (LvMMD2) beside the associated marker. This gene encodes the progestin and AdipoQ receptor 10 (PAQR10) protein. We further investigate the polymorphisms of LvMMD2 and their association with body weight of L. vannamei. By resequencing the coding region of LvMMD2, a total of 8 SNPs were identified, including 6 synonymous mutations and 2 nonsynonymous mutations. Association analyses based on a population of 322 individuals revealed that several SNPs located in the coding region of LvMMD2 were significantly associated with the body weight, especially the nonsynonymous mutation named as MMD_5 contributed the most association to the trait and it could explain 10.5% of phenotypic variance. In addition, several genes involved in growth and development have been identified as LvMMD2-interacting genes. These findings strongly suggested that LvMMD2 might be an important gene regulating the shrimp growth. More importantly, the MMD_5 could be a promising candidate locus for marker-assisted selection (MAS) of the body weight in L. vannamei.