本文選題：Tm-1-like(Tm-1L)基因 + 水平基因轉移��； 參考：《揚州大學》2017年碩士論文

【摘要】：陸生植物的起源是地球生命進化史上的最為重要的事件之一,對現代陸地生態(tài)系統的形成具有至關重要的作用。陸生植物起源于水生的綠藻,在由水生到陸生的進化過程中,陸生植物祖先面臨著干旱、多變的溫度、增強的紫外線輻射等諸多不利因素,此外陸生植物還要面對與水生環(huán)境截然不同的微生物環(huán)境,因此,植物在登陸陸地的過程中需要進化出新的基因和新表型特征來適應陸地的生存環(huán)境。番茄(Solanum lycopersium L.)的Tm-1基因是番茄花葉病毒(Tomatomosaic virus,ToMV)的重要抗性基因,其抗性等位基因來源于野生番茄(S.habrochaite)。Tm-1基因編碼的蛋白質序列與已知抗性基因(R gene)具有截然不同的序列特征,該基因編碼的蛋白質能特異地結合ToMV的復制蛋白并對RNA復制起到抑制作用,從而表現出對番茄花葉病毒的抗性。對該基因的序列相似性分析發(fā)現其在已測序陸生植物基因組中普遍存在同源基因,并表現出高度的序列保守性。該基因在植物中的同源基因編碼的蛋白質具有相似的結構域特征,其N-末端均具有UPF0261結構域,而C-末端均具有TBST結構域。盡管該基因在番茄中的抗病作用已經明確,但其起源和進化模式還不清楚,尤其是其在其他植物中的功能尚有待進一步挖掘。本文基于生物信息學方法,采用序列相似性和系統進化樹相結合的方法揭示植物Tm-1-like(Tm-1L)基因的起源機制;進一步在玉米中通過RT-PCR方法分析該基因的組織器官和非生物逆境表達模式。研究結果將為揭示植物Tm-1L基因的起源和進化模式,并為在其他植物物種中對該基因開展功能鑒定提供借鑒。主要研究內容和結果包括:(1)序列相似性分析發(fā)現已測序的鏈形植物(包括陸生植物和輪藻)中均具有Tm-1L基因,并且序列具有高度保守的特征,而在鏈形植物的祖先物種綠藻和紅藻中卻沒有同源基因。(2)植物Tm-1L基因編碼的蛋白質序列中具有2個高度保守的結構域:N-末端為UPF0261 結構域,C-末端是TIM-barrel-like signal transduction(TBST)結構域。進一步分析發(fā)現同時編碼這2個結構域的基因僅在鏈形植物中出現,而其他物種中的同源基因僅僅編碼其中1個結構域的蛋白質序列。(3)分別以包含UPF0261和TBST結構域的代表性蛋白質序列構建了系統進化樹,結果發(fā)現植物編碼UPF0261結構域的基因和編碼TBST結構域的基因是通過2次不同的水平基因轉移(horizontal gene transfer,HGT)事件起源的,其中UPF0261基因的假定供體是細菌,而TBST基因的假定供體是真菌或原核生物。植物中具有UPF061和TBST結構域的蛋白質序列被同一基因編碼,可能是這2個基因之間的一次基因融合(gene fusion)的結果。(4)對UPF0261和TBST蛋白質序列進行了共進化(co-evolution)分析,結果發(fā)現在真菌、細菌和古菌中UPF0261和TBST蛋白質之間均存在明顯的共進化特征,表明UPF0261和TBST基因之間可能具有功能的互補性,并存在交互作用。(5)基于對植物Tm-1L基因的起源和進化分析,本文提出了一種新的基因起源機制,即:存在交互作用的多個基因可以通過多次獨立的水平基因轉移事件進入受體基因組,進一步在受體基因組中通過基因融合形成一個基因,并行使功能。(6)為初步揭示該基因在玉米中的潛在功能,本研究分別在苗期和抽雄期對該基因的組織表達模式進行了分析,結果發(fā)現苗期該基因在幼莖中表達量最高,而抽雄期則在雌穗中表達量最高。(7)進一步分析了玉米Tm-1L基因在非生物逆境條件下的表達模式,結果發(fā)現該基因在干旱、低溫、高溫和高鹽等非生物逆境脅迫下,表達量顯著增強。此外,該基因的表達還受到ABA的誘導。研究結果表明該基因可能參與植物對非生物逆境脅迫的響應。
[Abstract]:The origin of terrestrial plants is one of the most important events in the history of life evolution of the earth. It plays a vital role in the formation of modern terrestrial ecosystems. The terrestrial plants originated from aquatic green algae. In the process of evolution from aquatic to terrestrial, the ancestors of terrestrial plants faced drought, variable temperature, enhanced ultraviolet radiation and so on. In addition, the terrestrial plants need to face a different microbial environment which is completely different from the aquatic environment. Therefore, the plants need to evolve new genes and new phenotypic characteristics to adapt to the terrestrial environment in the process of landing land. The Tm-1 gene of Solanum lycopersium L. is Tomatomosaic virus, ToMV The genes encoded by the wild tomato (S.habrochaite).Tm-1 gene and the known resistance gene (R gene) have distinct sequence characteristics. The protein encoded by this gene can specifically bind the replicating egg white of ToMV and inhibit the replication of RNA, thus showing the opposite effect. Resistance of eggplant mosaic virus. The sequence similarity analysis of the gene found that the homologous genes existed in the genome of the sequenced terrestrial plants and showed a high sequence conservatism. The gene encoded by homologous genes in the plant had similar domain characteristics, and the N- end of the gene had a UPF0261 domain, and the end of C- was the end of the gene. All of them have TBST domain. Although the resistance of the gene is clear in tomato, its origin and evolution model is not clear, especially its function in other plants remains to be further excavated. Based on the bioinformatics method, the combination of sequence similarity and phylogenetic tree is used to reveal plant Tm-1-like (T). M-1L) the mechanism of gene origin; further analysis of the gene organ and abiotic stress expression pattern in Maize by RT-PCR method. The results will reveal the origin and evolution pattern of the plant Tm-1L gene and provide reference for the functional identification of the gene in other plant species. The main contents and results include the main contents and results. (1) sequence similarity analysis found that the sequenced chain plants (including terrestrial plants and algae) have Tm-1L gene, and the sequence is highly conserved, but there are no homologous genes in the ancestral species of the chain plant green algae and red algae. (2) the protein sequences encoded by the plant Tm-1L gene have 2 highly conserved structures. Domain: the N- end is the UPF0261 domain, and the end of the C- is the TIM-barrel-like signal transduction (TBST) domain. Further analysis shows that the genes encoding the 2 domains are found only in the chain plants, and the homologous genes in other species only encode the protein sequences of the 1 domains. (3) include UPF0261 and TBST nodes, respectively. The representative protein sequence of the domain constructs the phylogenetic tree. The results show that the gene and the gene encoding the TBST domain of the UPF0261 domain are derived from the 2 different horizontal gene transfer (horizontal gene transfer, HGT), in which the UPF0261 gene assumes that the donor is a bacterium, and the presumed donor of the TBST gene is the donor. Fungi or prokaryotes. Protein sequences with UPF061 and TBST domains in plants are encoded by the same gene, which may be the result of one gene fusion (gene fusion) between the 2 genes. (4) the sequence of UPF0261 and TBST proteins was coevolved (co-evolution), and the results were found in fungi, bacteria and paleo bacteria in UPF0261 and TBST. There are obvious coevolution characteristics between proteins, indicating that the UPF0261 and TBST genes may have functional complementarity and interaction. (5) based on the analysis of the origin and evolution of plant Tm-1L genes, this paper proposes a new gene origin mechanism, that is, multiple genes stored in interaction can be independent by many times. The horizontal gene transfer event enters the receptor genome, further forms a gene through gene fusion in the receptor genome, and exercises its function. (6) the potential function of the gene in maize is preliminarily revealed. This study analyzed the pattern of the gene in the seedling stage and the male stage, and the results were found at the seedling stage. The expression of the young stem was the highest, while the male stage was the highest in the female ear. (7) the expression pattern of the maize Tm-1L gene under abiotic stress was further analyzed. The results showed that the gene was significantly increased under the abiotic stress of drought, low temperature, high temperature and high salt. In addition, the expression of the gene was also induced by ABA. The results suggest that the gene may be involved in the response of plants to abiotic stress.
【學位授予單位】：揚州大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：Q943.2

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本文編號：2001409