綠豆發芽過程中子葉粒線體DNA之複雜性和DNA複製型式相關性之探討

Correlation between mtDNA complexity and mtDNA replication mode in developing cotyledon mitochondria during mung bean seed germination

成寧(Ning Cheng)

指導教授 ： 戴華 ； 林納生

共同指導教授 ： 鄭石通(Shih-Tong Jeng)

國立臺灣大學/生命科學院/植物科學研究所/博士(2016年)

https://doi.org/10.6342/NTU201603771

摘要

綠豆子葉粒線體DNA結構、型態和複雜性在綠豆種子發芽過程中呈現高度的動態變化，本研究目的在藉此了解植物粒線體DNA複雜性和複製過程的相關性。研究結果顯示，在早期子葉發育過程中，粒線體中短的DNA片段轉換為長的線性DNA以及花瓣狀結構的DNA。隨著DNA在子葉發育過程中複製活力越高，伴隨著越來越複雜的花瓣狀結構出現。在DNA複製過程中，複製叉會出現在這種花瓣結構核心周圍部分。以低溫處理種子或低溫儲存已純化之子葉粒線體DNA，會誘導DNA轉成長線狀結構，花瓣結構的核心部分消失。這種長線結構上可明顯觀察到D環 (D-loop)、霍利迪交叉 (Holliday junction)等複製結構。長線結構型態的DNA總長度可能超過花瓣結構型態的長度30倍以上。本研究推測這種花瓣核心結構包含大量聚集的DNA，是依賴重組複製模式(Recombination dependent replication, RDR)中DNA複製的主要場所以及複製起點位置。在花瓣結構上出現的衛星核心結構代表另一個重新開始的複製起點，進而形成巨大且複雜、具有大量複製中間體的粒線體DNA分子結構。此研究結果可證實花瓣狀DNA結構是植物粒線體複製之中間產物，並且確定粒線體DNA是依循依賴重組複製模式進行複製。

關鍵字

植物粒線體 ； 粒線體發育 ； 粒線體DNA ； 粒線體DNA複製 ； 綠豆子葉 ； 依賴重組複製模式, 花瓣狀DNA結構

並列摘要

The highly dynamic changes in mitochondrial DNA (mtDNA) conformation, structure and complexity correspond to the activity of mtDNA recombination dependent replication (RDR). This study aimed to elucidate the interrelationship between mtDNA replication and genesis of the multi-genomic, highly complex structure of plant mtDNA in mung bean cotyledons. The results suggest that short DNA fragments convert to longer linear and rosette structures early in the development of cotyledon mitochondria. Consequently, a large number of rosette structures appear, with simultaneous elevation of mtDNA synthesis. A fork-like structure near the rosette core appears during mtDNA replication. With in vivo prolonged-cold incubation or in vitro freeze-thaw treatment, the rosette structure is converted to a much longer linear DNA structure and the rosette core disappears. This large linear DNA with displacement loops, Holliday junctions and other structures attached may increase in size more than 30 times as compared to the original rosette entity. The rosette core may consist of condensed mtDNA and play an initial and central role in RDR. The satellite cores in the rosette structure may represent the re-initiation sites of mtDNA RDR in the same parental molecule. Consequently, highly complex and giant mitochondrial DNA molecules, representing RDR intermediates, are formed in vivo. The core-and-rosette structures represent replicating DNA and almost certainly use RDR.

並列關鍵字

mtDNA replication ； mitochondrial development ； mtDNA complexity ； mtDNA rosette ； mung bean (Vigna radiata) ； plant mitochondrial DNA ； recombination- dependent replication ； rosette core

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