本文選題：鯨類 + 三酰甘油��； 參考：《南京師范大學》2016年博士論文

【摘要】：鯨類(Cetacea)是一類在進化上具有十分重要和特殊意義的次生性水生動物,約56-53百萬年前其祖先從陸地重返海洋,伴隨著形態(tài)的巨大改變和快速地適應輻射,形成了豐富多樣的現(xiàn)生鯨類。從陸地重返海洋,鯨類面臨的首要挑戰(zhàn)就是生活介質的改變,由原先的空氣變?yōu)榱怂?而水這種高效的熱傳導體,在相同的溫度下,從體內帶走熱量的速度比空氣快25倍。因此對于鯨類而言,一方面面臨著嚴重的熱量喪失,必須獲取足夠的保溫物質；另一方面面臨環(huán)境變遷、季節(jié)更替所造成的食物短缺,必須形成獨特的代謝機制以獲取足夠的能量。為了應對這些挑戰(zhàn),鯨類的鯨脂層較其他陸生哺乳動物顯著增厚。這個改變在鯨類適應水生生境的過程中具有非常重要的意義,增厚的鯨脂層不僅能夠起到保溫、保證身體流線型、增加浮力和促進運動等作用,而且更為重要的是能通過脂肪代謝提供機體所需的能量和淡水。顯然,鯨類在適應水生生境的過程中,已經形成了完善的鯨脂層增厚及相關的脂肪代謝機制。然而,這一適應的分子進化機制尚不清楚。本研究首次對鯨類脂肪消化、鯨脂層增厚和脂質代謝通路三個方面的基因進行了分子進化分析,試圖闡明鯨類脂肪代謝適應性進化歷史,并從分子水平上揭示脂肪代謝相關基因與鯨類水生適應之間的關系。論文第二章,研究了在脂肪的消化、溶解和吸收過程中起關鍵作用的四個消化酶基因(PNLIP、LIPC、LIPF和CYP7A1)在鯨類和其他陸生哺乳動物中的分子進化。結果表明,脂肪消化酶的三個關鍵基因(CYP7A1、LIPF和PNLIP)在鯨類中受到了強烈的正選擇作用,提示這些基因發(fā)生了適應性進化,有助于提高對于食物中脂肪物質消化和吸收的能力,從而促進了鯨類食性的轉變。同時,CYP7A1和PNLIP兩個消化酶基因還在鯨類和食肉目兩個枝之間檢測到了3個平行／趨同位點,進一步說明了鯨類中的脂肪消化酶基因發(fā)生了適應性進化,而且表明鯨類和食肉目動物在脂肪消化方面存在相似性。論文第三章,首次在鯨類代表物種和其他哺乳動物中研究了88個三酰甘油代謝相關基因的分子進化,揭示了三酰甘油代謝相關基因的適應性進化在鯨脂層增厚過程中的關鍵作用。研究結果發(fā)現(xiàn)88個候選基因中的41個被檢測到受正選擇作用,這些基因分別參與三酰甘油的合成、分解和調控等過程。三酰甘油代謝相關基因存在如此廣泛的正選擇信號,可能與鯨類鯨脂層的溫度調節(jié)、浮力控制、保持身體流線型、代謝能量儲存和促進運動等重要功能有關。有趣的是,一些阻止脂解的調控基因在鯨類中也檢測到了顯著的正選擇證據,表明鯨類已經進化出了一種有效機制防止鯨脂層被無限制降解,這對鯨類在禁食期維持鯨脂層厚度尤為重要。這些結果表明,鯨類存在有效且復雜的機制來保證鯨脂層維持合適厚度,從而更好的適應水生生活；同時也表明“肥胖”對于人類而言與多種慢性疾病有關,但是對于鯨類則是一種健康狀態(tài)。論文第四章,對KEGG數據庫中整個脂質代謝通路的327個基因進行了研究,全面揭示了脂質代謝通路基因在鯨類水生適應進化過程中的重要作用。結果發(fā)現(xiàn),在鯨類中受正選擇作用的149個基因分別位于脂質代謝通路中的15個分通路,并且鯨類的各個枝系都檢測到了正選擇基因,提示鯨類脂質代謝通路基因發(fā)生了持續(xù)的適應性進化。結合各個代謝途徑的功能,表明脂質代謝通路中TAG合成、脂肪酸分解及多不飽和脂肪酸的代謝等功能都得到了增強,為鯨類更好的適應水生生境并輻射到全球各個水域起到了積極的推動作用。
[Abstract]:Cetacean (Cetacea) is a very important and special class of secondary aquatic animals. About 56-53 million years ago, its ancestors returned from land to sea, accompanied by great changes in morphology and rapid adaptation to radiation, forming rich and diverse cetaceans. The primary challenge facing whales was to live from land to sea. The change in the medium is changed from the original air to the water, and the high efficient heat transfer conductor, which takes away the heat from the body at the same temperature, is 25 times faster than the air. Therefore, for cetaceans, on the one hand, it faces severe heat loss and has to obtain sufficient thermal insulation; on the other hand, it faces environmental changes and seasonal changes. In order to respond to these challenges, cetacean blubber layers are significantly thicker than other terrestrial mammals. This change is of great significance in the process of cetacean adaptation to aquatic habitats. The thickened blubber layer not only protects the body, but also ensures the body. Streamlining, increasing buoyancy and promoting movement, and more important is the energy and fresh water that can be provided through fat metabolism. Obviously, cetacean has formed a perfect blubber layer thickening and related lipid metabolism mechanism in the process of adapting to aquatic habitats. However, the molecular evolutionary mechanism of this adaptation is not yet clear. In this study, the three genes of cetacean fat digestion, blubber layer thickening and lipid metabolism pathway were analyzed for the first time in order to elucidate the evolutionary history of cetacean fat metabolism, and to reveal the relationship between fat metabolism related genes and cetacean aquatic adaptation from the molecular level. In the second chapter, the fat was studied. Molecular evolution of four digestive enzyme genes (PNLIP, LIPC, LIPF and CYP7A1) in cetaceans and other terrestrial mammals during digestion, dissolution and absorption. The results showed that three key genes (CYP7A1, LIPF, and PNLIP) of fat Digestis (CYP7A1, LIPF and PNLIP) were strongly selective in cetaceans, suggesting that these genes were appropriate. Sexual evolution helps to improve the ability to digest and absorb fatty substances in food, thus promoting the transformation of cetaceans. At the same time, the two digestive enzyme genes of CYP7A1 and PNLIP also detected 3 parallel / convergent loci between cetaceans and two branches of carnivores, which further indicated that the fat digestible enzyme gene in cetaceans was suitable. In the third chapter, the molecular evolution of 88 three glycerol metabolism related genes was first studied in cetacean representative species and other mammals, and the adaptive evolution of three acyl glycerol metabolism related groups was revealed in the blubber layer thickening process. The results showed that 41 of the 88 candidate genes were detected by positive selection. These genes were involved in the synthesis, decomposition and regulation of three glycerol respectively. The three glycerol metabolism related genes had such a wide selection signal, which might be associated with the temperature regulation, buoyancy control and body flow of whale whale fat layer. It is interesting that some regulatory genes that prevent lipolysis have also been identified in cetaceans with significant positive evidence that cetacean has evolved an effective mechanism to prevent the blubber layer from being degraded without restriction, which is particularly important for Cetacean blubber thickness during the fasting period. These results suggest that cetacean has an effective and complex mechanism to ensure that the blubber layer maintains appropriate thickness to better adapt to aquatic life; it also indicates that "obesity" is associated with a variety of chronic diseases for humans, but is a healthy state for cetaceans. In the fourth chapter, the whole lipid metabolism in the KEGG database 327 genes in the pathway have been studied to reveal the important role of the lipid metabolism pathway in the adaptation and evolution of cetacean aquatic. It is found that the 149 genes of positive selection in cetacean are 15 pathways in the lipid metabolism pathway, and all the branches of cetaceans have detected the positive selection genes. The genes of cetacean lipid metabolism pathway have sustained adaptive evolution. Combining the functions of various metabolic pathways, it shows that the functions of TAG synthesis, fatty acid decomposition and polyunsaturated fatty acid metabolism in the lipid metabolic pathway have been enhanced, which are active for cetaceans to adapt to aquatic habitats and to radiate all waters around the world. Push the effect.

【學位授予單位】：南京師范大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：Q953

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