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標題: 玉米B染色體之演化
Evolution of Maize B Chromosome
作者: 鄭雅銘
關鍵字: 基礎研究;maize B chromosome;生物科學類, 農藝;玉米B 染色體;演化;異染色質;常染色質;B-10L 易位染色體;同源演化分析;cDNA-AFLP;evolution;heterochromatin;euchromatin;B-10Ltranslocation;phylogenetic analysis;cDNA-AFLP
The maize B chromosome has been identified for nearly a century, but its evolutionis still elusive. The B chromosome arises not as a product of natural selection; therefore itis an ideal material for studying chromosome evolution. The objective of this proposal isto gain a better understanding of the B evolution. This goal will be achieved in twodirections: heterochromatic and euchromatic approaches. A previously identifiedCL-repeat will be used to study the evolution of heterochromatin on the B long arm. TheCL-repeat is repetitive and specific to three distal heterochromatic (DH) regions locatedin the B long arm. Thus, its mutational variants uncovered from each DH region—usingtertiary trisomes and hypoploids of five B-10L translocations—would provide salientinformation for conducting a phylogenetic analysis to elucidate the evolution path of thethree DH regions, which will be substantiated by results of the structure variant andSouthern fragment analysis. On the other hand, we will use the cDNA-amplifiedfragment length polymorphism (cDNA-AFLP) technique to isolate cDNA from theeuchromatic regions of the B chromosome. Characterization of these B-cDNAs will beexploited for the possible implication on its evolution. The information garnered from thetwo regions will eventually shed light on the origin of the B chromosome which, in turn,may be conducive to understanding of chromosome evolution in general.

玉米B 染色體被發現已經將近一世紀,但是對其演化過程依然了解有限。B 染色體的產生沒有經過自然的篩選,因此是一個研究染色體演化的理想材料。本計畫之目的為,對B 染色體之演化有更多的了解。為了達成此目的,分別從異染色質區與常染色質區兩個方向來進行。首先,將利用先前發現的CL-repeat 研究異染色質區的演化。CL-repeat 是重複性序列且專一存在於B 染色體長臂的三個異染色質區上,因此利用五個B-10L 易位染色體所產生的三級三染體及亞倍體,可以從個別的異染色質區分離出CL-repeat 的突變序列,將這些序列進行同源演化分析,可以藉此推論出三個異染色質區的演化過程;此演化過程也預期能由CL-repeat 的構造變異及Southern 片段獲得驗證。另一方面,本計劃將利用cDNA-AFLP 技術分離玉米B 染色體常染色質區上的cDNA 序列,藉由分析這些B 染色體的cDNA,可以了解B 染色體常染色質區的可能演化。本研究計劃的結果最終可以解釋玉米B 染色體的來源,也可以幫助我們了解一般染色體的演化。
其他識別: NSC99-2311-B005-003-MY3
Appears in Collections:農藝學系

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