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

【摘要】：鯨類(Cetacea)是一類在進(jìn)化上具有十分重要和特殊意義的次生性水生動(dòng)物,約56-53百萬(wàn)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(yīng)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(zhì)的改變,由原先的空氣變?yōu)榱怂?而水這種高效的熱傳導(dǎo)體,在相同的溫度下,從體內(nèi)帶走熱量的速度比空氣快25倍。因此對(duì)于鯨類而言,一方面面臨著嚴(yán)重的熱量喪失,必須獲取足夠的保溫物質(zhì)；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(dú)特的代謝機(jī)制以獲取足夠的能量。為了應(yīng)對(duì)這些挑戰(zhàn),鯨類的鯨脂層較其他陸生哺乳動(dòng)物顯著增厚。這個(gè)改變?cè)邛L類適應(yīng)水生生境的過(guò)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(jìn)運(yùn)動(dòng)等作用,而且更為重要的是能通過(guò)脂肪代謝提供機(jī)體所需的能量和淡水。顯然,鯨類在適應(yīng)水生生境的過(guò)程中,已經(jīng)形成了完善的鯨脂層增厚及相關(guān)的脂肪代謝機(jī)制。然而,這一適應(yīng)的分子進(jìn)化機(jī)制尚不清楚。本研究首次對(duì)鯨類脂肪消化、鯨脂層增厚和脂質(zhì)代謝通路三個(gè)方面的基因進(jìn)行了分子進(jìn)化分析,試圖闡明鯨類脂肪代謝適應(yīng)性進(jìn)化歷史,并從分子水平上揭示脂肪代謝相關(guān)基因與鯨類水生適應(yīng)之間的關(guān)系。論文第二章,研究了在脂肪的消化、溶解和吸收過(guò)程中起關(guān)鍵作用的四個(gè)消化酶基因(PNLIP、LIPC、LIPF和CYP7A1)在鯨類和其他陸生哺乳動(dòng)物中的分子進(jìn)化。結(jié)果表明,脂肪消化酶的三個(gè)關(guān)鍵基因(CYP7A1、LIPF和PNLIP)在鯨類中受到了強(qiáng)烈的正選擇作用,提示這些基因發(fā)生了適應(yīng)性進(jìn)化,有助于提高對(duì)于食物中脂肪物質(zhì)消化和吸收的能力,從而促進(jìn)了鯨類食性的轉(zhuǎn)變。同時(shí),CYP7A1和PNLIP兩個(gè)消化酶基因還在鯨類和食肉目?jī)蓚�(gè)枝之間檢測(cè)到了3個(gè)平行／趨同位點(diǎn),進(jìn)一步說(shuō)明了鯨類中的脂肪消化酶基因發(fā)生了適應(yīng)性進(jìn)化,而且表明鯨類和食肉目動(dòng)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(dòng)物中研究了88個(gè)三酰甘油代謝相關(guān)基因的分子進(jìn)化,揭示了三酰甘油代謝相關(guān)基因的適應(yīng)性進(jìn)化在鯨脂層增厚過(guò)程中的關(guān)鍵作用。研究結(jié)果發(fā)現(xiàn)88個(gè)候選基因中的41個(gè)被檢測(cè)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(diào)控等過(guò)程。三酰甘油代謝相關(guān)基因存在如此廣泛的正選擇信號(hào),可能與鯨類鯨脂層的溫度調(diào)節(jié)、浮力控制、保持身體流線型、代謝能量?jī)?chǔ)存和促進(jìn)運(yùn)動(dòng)等重要功能有關(guān)。有趣的是,一些阻止脂解的調(diào)控基因在鯨類中也檢測(cè)到了顯著的正選擇證據(jù),表明鯨類已經(jīng)進(jìn)化出了一種有效機(jī)制防止鯨脂層被無(wú)限制降解,這對(duì)鯨類在禁食期維持鯨脂層厚度尤為重要。這些結(jié)果表明,鯨類存在有效且復(fù)雜的機(jī)制來(lái)保證鯨脂層維持合適厚度,從而更好的適應(yīng)水生生活；同時(shí)也表明“肥胖”對(duì)于人類而言與多種慢性疾病有關(guān),但是對(duì)于鯨類則是一種健康狀態(tài)。論文第四章,對(duì)KEGG數(shù)據(jù)庫(kù)中整個(gè)脂質(zhì)代謝通路的327個(gè)基因進(jìn)行了研究,全面揭示了脂質(zhì)代謝通路基因在鯨類水生適應(yīng)進(jìn)化過(guò)程中的重要作用。結(jié)果發(fā)現(xiàn),在鯨類中受正選擇作用的149個(gè)基因分別位于脂質(zhì)代謝通路中的15個(gè)分通路,并且鯨類的各個(gè)枝系都檢測(cè)到了正選擇基因,提示鯨類脂質(zhì)代謝通路基因發(fā)生了持續(xù)的適應(yīng)性進(jìn)化。結(jié)合各個(gè)代謝途徑的功能,表明脂質(zhì)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(qiáng),為鯨類更好的適應(yīng)水生生境并輻射到全球各個(gè)水域起到了積極的推動(dòng)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(xué)位授予單位】：南京師范大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：Q953

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