International Journal of Marine Science, 2025, Vol.15, No.5, 233-244 http://www.aquapublisher.com/index.php/ijms 241 energy reserves under high temperature stress and accelerate anaerobic glycolysis pathways to provide ATP in the short term, but in the long term it will cause energy overdraft (Zhang et al., 2022). 7.2 Structural variation and expression regulation of heat shock protein (HSP)-related genes Heat shock protein is one of the main forces of organisms to resist high temperature stress. The structural variation and expression regulation of its genes in the oyster genome play a key role in heat resistance adaptation. The biggest feature of the Oyster HSP gene family is its extremely rich membership. Taking the HSP70 family as an example, about 88 HSP70 genes were identified in the Pacific oyster genome, several times that of model organisms such as mammals. Most of these HSP70 genes are distributed in clusters on chromosomes through tandem repetition. The number of HSP70 genes in Ostrea denselamellosa is significantly smaller than that of other oysters, which may explain its sensitivity to high temperatures. This once again confirms the close relationship between structural variation (gene replication or contraction) and heat-resistant phenotype. In addition to differences in gene copy number, high temperature adaptation also depends on the effectiveness of HSP gene regulation. Structural variation also participates in this regulation and improvement. Some studies have found that different oyster lines or subspecies have slight insertion/deletion variants in the promoter region of the HSPgene, which can affect the transcription factor binding site and thus change the initiation efficiency of HSPgenes under thermal stimulation (Liu et al., 2020; Wang et al., 2023). 7.3 Case implications: the role of structural variation in temperature adaptation and climate change response The high-temperature adaptation cases further highlight the core role of genomic structural variation in the environmental adaptation of oysters, and adaptive structural variation is the "buffer" for species survival in the context of climate change. As global warming, extreme events in seawater temperature will be more frequent. Populations with rich structural variation have greater genetic diversity to deal with these changes. Repeated evolution utilizes structural variations to adapt to different environments is a common pathway for organisms to adapt to different environments (Modak et al., 2021). As shown in the study of Stickleback fish, prickly insects and other organisms, when different populations or species adapt to similar environments, similar types of structural mutations often appear in parallel. Structural variation research can serve the protection and breeding of oysters. Using genomic means to screen wild oyster populations and identify structural variation sites related to key traits such as heat tolerance, helps to determine which populations have higher adaptability potential and should be given priority. At the same time, these key structural variants can also be used for the breeding of oyster stress-resistant strains. For example, individuals enriched with amplified variants of heat-resistant genes for breeding can shorten the cycle of nurturing new high-temperature resistant varieties (Ding et al., 2020). 8 Application Prospects of Research on Genome Structural Variation of Oysters 8.1 Potential applications in aquatic breeding Research results on genomic structural variation are expected to play an important role in oyster genetic breeding. Using SV as a new molecular marker for assisted breeding selection is a promising direction. Currently, oyster breeding is mainly based on phenotypic selection and a small number of SNP markers, while structural variant markers may capture some sources of trait variants that SNP cannot cover. Through genome-wide association analysis (GWAS), we can lock in these SV sites associated with the target trait and design specific primers for breeding population screening. Secondly, structural variation research can reveal hidden adverse variants and help improve germplasm. Long-term artificial breeding may cause certain harmful structural mutations to accumulate in breeding populations, which may reduce population resilience. Monitoring SVs in breeding populations by genome sequencing allows us to timely detect and eliminate these potentially adverse variants to maintain genetic health. Structural variation research can also be used to optimize hybrid breeding strategies. Oyster hybridization is often used to introduce trait hybrid advantages, such as Kumamoto oyster x long oyster hybridization performs well in stress resistance and growth. Genomic analysis found that these hybrid progeny may carry different combinations of structural variants of parents at the same time, such as inheriting HSP amplification from one parent and carrying metabolic gene regulatory variants from another parent, thereby achieving complementary advantages.
RkJQdWJsaXNoZXIy MjQ4ODYzNA==