Knowledge Management System Of Institute of Oceanology, Chinese Academy of Sciences
|Alternative Title||The impact of selection of heat stress on economic characters and its mechanism for Pacific oyster Crassostrea gigas|
|Place of Conferral||中国科学院海洋研究所|
|Keyword||长牡蛎 人工选育 热耐受性 遗传结构 度夏存活|
为解析一代应激选择对牡蛎遗传结构的影响并进一步揭示热耐受性的遗传机制,我们比较了选育群体F1代高温热激后存活个体与未选育群体热激后死亡个体的遗传结构。利用简化基因组测序的方法对两群体（每个群体各50只牡蛎）进行遗传结构分析，并且定位到受选择区域及候选基因，并检测候选基因在热激下的表达分化差异。测序和质控后得到379002个SNP位点。基于高质量的SNP位点，系统发育树将两群体分为3个聚类，群体结构分析也将100个个体分为3个群组。PCA的结果与系统发育树和群体结构分析结果一致。这些结果表明选育群体与对照群体的遗传结构出现了分化，但鉴于只经过一代选育，因此分化是很有限的。根据FST和θπ值确定了115个受选择区域，包含472个基因。对472个基因进行GO富集，得到7个显著的GO注释（p < 0.05），其包含了18个受选择基因（实验室已有研究表明BAG4在温度适应中可能具有重要作用，因此BAG4也被选为候选基因），候选基因的表达结果显示，在两群体中，有8个基因（IF4A2, IF6, EIF3A, MANBA, DDX43, RECS, CAT2, BAG4）在热激过程中表达量发生了分化，说明这些基因的表达分化参与了选育群体与对照群体的分化，而且其中6个基因在选育群体中表现出低的基础表达和高的诱导表达，表明大部分选育群体的基因表达具有更高的可塑性。生物的热耐受性对预测生物响应气候变化的潜在适应能力起着重要作用，我们的结果为牡蛎的热耐受研究提供了分子基础。
Oyster is one of the most important worldwide economic species. Mass mortality was happened during summer and has become a serious threat to the global oyster aquaculture industry. Elevating temperature is considered as one of the most important abiotic factors causing the summer mortality of oysters. Therefore, it is necessary to explore the mechanism for thermal adaptation and thermotolerance of oysters. We initiated an artificial selective breeding program aimed at increasing survival rate of C. gigas during the summer since 2017. we collected phenomics and genomics evidence to identify discrepant responses to temperature elevation between thermal tolerance oysters after one-generation of selection, and to elucidate the potential molecular mechanisms for heat tolerance in oysters.
1. Differences in thermotolerance and physiological responses between selected F1 population and natural population.
Parental selection is based on acute thermal tolerance under controlled heat stress (42 ℃, 1h) to ensure selection intensity (37%). We compared the difference in ability of thermal adaptation between the selected F1 and natural population. Specifically, the growth, respiration rate, heat tolerance and physiological indicators was measured between 6-month-old selected F1 and natural population. The summer mortality and growth was evaluated to verify practical significance for aquaculture industry of artificial selection breeding in thermotolerance when the oysters was 19-month-old. The results showed that there was no significant difference in growth after one-generation selection between selected and control population. The thermal tolerance of the progeny post exposure to acute heat stress in the selected population was significantly higher than that in the natural population even only after one-generation selection, suggesting the thermotolerance of selected oysters was improved. This result was in line with the results under field conditions. The respiration rate of the selected population at 38 ℃ was significantly higher than that of 20 ℃, while the respiration rate of the natural population was significantly increased at 35 ℃, indicating that the natural population was more sensitive to high temperature stress, selected population has a greater capacity of oxygen supply. The results of physiological indicators showed that the selected oysters had higher enzyme activities related to metabolism and anti-oxidation (PK, SOD) during the heat stress, indicating that selected population had stronger antioxidant capacity. It has been proved by various means that the thermotolerance of oyster has been significantly improved after one generation selection of acute heat stress, which proves that the breeding strategy is effective.
2. Genetic evolution analysis of thermotolerant population and heat-sensitive population
In order to analyze the molecular mechanism of oysters’ thermal adaptability, the survival individuals of selected population were considered as thermotolerant population, the dead individuals of natural population after heat stress were considered as heat-sensitive population (control). Specific-locus amplified fragment sequencing (SLAF-seq) was used to analysis the genetic structure of the two population (50 individuals per population). We also identified the selected region and candidate genes. The gene expression under heat shock was analyzed. After sequencing and quality control, 379002 SNPs were obtained. Based on high quality SNPs, phylogenetic tree divides the two populations into 3 clusters. The results of PCA verified the results of phylogenetic tree and population structure analysis. These results suggested that the restricted genetic divergence between the oysters with one-generation selection and un selected oysters. The 115 selected region and 472 genes was determined based on FST and θπ values, and 18 candidate genes were obtained by GO enrichment (BAG4 was selected according previous studies that suggests it may play important role in temperature adaptation). Eight genes (IF4A2, IF6, EIF3A, MANBA, DDX43, RECS, CAT2, and BAG4) diverged in transcriptional expression response to heat stress. Six of genes showed lower basal expression and higher induced expression under heat stress in thermotolerant population compared with control population. which suggested higher plasticity of thermotolerant population. The heat tolerance of organisms plays an important role in prediction the potential ability to adapt climate change. Our results provide a molecular basis for researches on thermotolerance of oysters.
|MOST Discipline Catalogue||工学::生物工程|
|Funding Project||National Key R&D Program of China[2018YFD0900304] ; National Key R&D Program of China[2018YFD0900304]|
|Table of Contents|
|丁方芳. 高温应激选择对长牡蛎抗性等经济性状的影响及其机制研究[D]. 中国科学院海洋研究所. 中国科学院大学,2020.|
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