臺灣博碩士論文加值系統

雜種優勢(Hybrid vigor)是指不同物種間的雜交種(Hybrid)之生物特性優越於其父母。 雜種優勢的現象在植物和動物間相當普遍，然而，目前尚未有研究能徹底地解釋雜種優勢的分子機制。在此研究中，我們利用Saccharomyces cerevisiae及Saccharomyces bayanus此二種酵母菌來探討其雜種優勢。儘管這兩個物種已經由演化過程適應了不同的溫度範圍，但相較於親代，雜交種卻有更寬廣的溫度耐受範圍。溫度耐受性的擴展可被視為雜種優勢的一種。我們推測在不同的溫度下，雜交種擁有與親代不同的轉錄組(transcriptome)，而部分基因在雜交種裡的獨特表現可能是造成溫度耐受範圍擴展的原因。藉由DNA晶片(microarray)，我們比較雜交種與親代在不同溫度下的轉錄組。在高溫下，參與呼吸作用及粒線體轉譯機制的基因有著獨特的雜交種表現量；低溫下，與轉譯機制相關的基因有獨特的表現量。進一步的分析讓我們發現，在雜交種中有獨特表現量的基因，其大部分在親代的表現量已經有所差異，而且兩個親代之表現量差異性多為trans regulatory divergence所造成的。然而，雜交種獨特的基因表現與溫度耐受性的擴展間之連結需要進一步的實驗證明。

Hybrid vigor refers to the outperformance of intra- or interspecific hybrids compared to both parents in biological qualities, and is widespread in plants and animals. However, the molecular bases of hybrid vigor remain widely unexplored. Here, we studied the interspecific hybrid between mesophilic yeast Saccharomyces cerevisiae and cryophilic yeast Saccharomyces bayanus. While the two species have diverged in their fitness at distinct temperatures, the hybrid performed equally well as the better parent at two ends of the temperature spectrum. Furthermore, hybrid vigor was displayed as an extended range of temperature tolerance when compared to the parents. We speculated the novel gene expression patterns of hybrid at different temperatures were responsible for the extended temperature tolerance. Transcriptome comparison between hybrid and the two parents demonstrated that the hybrid displayed different sets of novel expression patterns at distinct temperatures: hybrid-specific expressions were enriched in genes relating to respiration and mitochondrial translation at high temperature, and in genes relating to translational machinery at low temperature. Majority of the hybrid-specific expressions belonged to genes with conditional trans-regulatory divergence between the parental species, suggesting the divergence in temperature sensing of the parents gave rise to novel expression of hybrid. Further evidence is required to demonstrate the importance of hybrid-specific expression in the hybrid vigor phenomena described. Our results provided insights on the novel regulatory changes upon hybridization of two different species, and hints to establish the connection between these regulatory changes to the hybrid vigor phenotypes.

口試委員會審定書i
誌謝ii
中文摘要iii
英文摘要iv~v
目錄 vi~vii
Chapter 1. Introduction 1~4
Chapter 2. Results 4~15
Chapter 3. Discussion 16~18
Chapter 4. Materials and Methods 18~23
Chapter 5. References 24~27
Figures 28~40
Supplementary figures 41~48

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