Although most fishes are ectothermic,some,including tuna and billfish,achieve endothermy through specialized heat producing tissues that are modified muscles.How these heat producing tissues evolved,and whether they s...Although most fishes are ectothermic,some,including tuna and billfish,achieve endothermy through specialized heat producing tissues that are modified muscles.How these heat producing tissues evolved,and whether they share convergent molecular mechanisms,remain unresolved.Here,we generated a high-quality genome from the mackerel tuna(Euthynnus affinis)and investigated the heat producing tissues of this fish by single-nucleus and bulk RNA sequencing.Compared with other teleosts,tuna-specific genetic variation is strongly associated with muscle differentiation.Single-nucleus RNA-seq revealed a high proportion of specific slow skeletal muscle cell subtypes in the heat producing tissues of tuna.Marker genes of this cell subtype are associated with the relative sliding of actin and myosin,suggesting that tuna endothermy is mainly based on shivering thermogenesis.In contrast,cross-species transcriptome analysis indicated that endothermy in billfish relies mainly on nonshivering thermogenesis.Nevertheless,the heat producing tissues of the different species do share some tissue-specific genes,including vascular-related and mitochondrial genes.Overall,although tunas and billfishes differ in their thermogenic strategies,they share similar expression patterns in some respects,highlighting the complexity of convergent evolution.展开更多
基金supported by the National Natural Science Foundation of China(32122021)the National Key Research and Development Program of China(2022YFC3400300)+1 种基金the 1000 Talent Project of Shaanxi Province to Q.Q.and K.W.,the Fundamental Research Funds of Northwestern Polytechnic Universitythe Open Foundation from Marine Sciences in the First-Class Subjects of Zhejiang(OFMS011)。
文摘Although most fishes are ectothermic,some,including tuna and billfish,achieve endothermy through specialized heat producing tissues that are modified muscles.How these heat producing tissues evolved,and whether they share convergent molecular mechanisms,remain unresolved.Here,we generated a high-quality genome from the mackerel tuna(Euthynnus affinis)and investigated the heat producing tissues of this fish by single-nucleus and bulk RNA sequencing.Compared with other teleosts,tuna-specific genetic variation is strongly associated with muscle differentiation.Single-nucleus RNA-seq revealed a high proportion of specific slow skeletal muscle cell subtypes in the heat producing tissues of tuna.Marker genes of this cell subtype are associated with the relative sliding of actin and myosin,suggesting that tuna endothermy is mainly based on shivering thermogenesis.In contrast,cross-species transcriptome analysis indicated that endothermy in billfish relies mainly on nonshivering thermogenesis.Nevertheless,the heat producing tissues of the different species do share some tissue-specific genes,including vascular-related and mitochondrial genes.Overall,although tunas and billfishes differ in their thermogenic strategies,they share similar expression patterns in some respects,highlighting the complexity of convergent evolution.
