International Journal of Aquaculture, 2025, Vol.15, No.5, 229-239 http://www.aquapublisher.com/index.php/ija 233 high-throughput sequencing. Compared with SSR, genotype interpretation of SNP is easier to standardize and is suitable for large-scale automated analysis (Du et al., 2010). In practical applications, SSR and SNP have their own advantages and disadvantages: SSR is suitable for paternity testing, small group linkage analysis, etc., and SNP is suitable for whole genome scanning, fine localization and breeding value prediction. 5.2 Key candidate genes identified by QTL and GWAS With the help of QTL mapping and GWAS analysis, researchers have unearthed candidate genes closely related to shrimp growth from numerous molecular marker signals. These genes have a variety of functions and cover different links of growth regulation (Ma et al., 2024). STEAP4 (Metal Reductase 4): Combining QTL localization with QTL expression (eQTL) analysis, the STEAP4 gene was found to be highly correlated with growth rate in vannabinoid shrimp. STEAP4 is involved in cellular iron ion metabolism, and the gene expression is significantly upregulated in rapidly growing individuals, and RNA interference experiments have shown that its silencing slows shrimp growth. Therefore, STEAP4 is considered to be one of the important regulatory genes that affect shrimp growth. Dnm1L (deoxycytidyl deaminase, or DCD): GWAS identified a significant association between SNP near the DCD gene and shrimp body weight. DCD plays a role in nucleotide metabolism, and mutation may affect the efficiency of DNA/RNA synthesis. PTK2 (non-receptor type tyrosine protein kinase): Similar to DCD, researchers found that some variations in the PTK2 gene were related to shrimp body weight. PTK2 is a cellular signaling molecule and may affect growth by regulating cell proliferation and differentiation signals. Given that growth processes involve multiple cellular signaling pathways, the association of this gene implies the signaling network composition of shrimp growth regulated (Yu et al., 2019). 5.3 Potential function of candidate genes in regulation of growth traits Based on the candidate genes identified above, the researchers further explored the mechanism of action of these genes in the regulation of shrimp growth. Overall, the genetic regulatory network for shrimp growth is very complex. These candidate genes each perform their own functions and may have interactions to form a multi-level regulatory system. Some candidate genes are directly involved in matter and energy metabolism, affecting the efficiency of nutrients required for shrimp growth. For example, STEAP4 metal reductase affects iron metabolism and cellular respiration. Research has found that inhibiting STEAP4 will reduce shrimp feeding and growth, which shows that energy metabolic activity is closely related to growth rate. Secondly, some candidate genes belong to signal transduction and cell cycle regulatory pathways. For example, PKC-δ, PTK2, Rap2a, etc., they belong to different signal cascades: PKC-δ participates in the MAPK pathway, PTK2 involves cell adhesion and proliferation signals, and Rap2a is a small G protein, which participates in growth factor stimulation response (Figure 1) (Zhu et al., 2022). When the genes of these signaling molecules mutate, the rate of cell proliferation and differentiation process downstream may change, affecting the growth of tissues and individuals. 6 Case Analysis: Study on Growth Traits of Chinese Prawns 6.1 Research progress on QTL localization of growth-related traits of Chinese shrimp Chinese prawns were once the pillar species of coastal farming in northern China, and the genetic improvement of their growth traits is related to industrial revitalization. After the disease hit the industry hard at the end of the last century, scientists carried out the family breeding of Chinese prawns, and in 2003 it became China's first new breed of marine aquaculture animals - "Huanghai No. 1" Chinese prawns. For this breeding line, early research constructed a genetic linkage map of Chinese shrimp, and QTL analysis of growth traits was performed for the first time. Results QTLs related to body weight and body length were found on several chromosomal segments, and some SSR markers closely linked to QTL were screened out (Liu et al., 2010). These markers were once believed to be used for molecular assisted breeding of Chinese shrimp. In the past five years, with the promotion of molecular tools in aquatic products, there have been new trends in the study of growth traits of shrimp in China. The first is the study of population genetic diversity and differentiation. More importantly, they identified a group of SNP sites with significant frequency differences between breeding and wild populations (significant to Fst).
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