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Title: Localization of Centromere and Telomere Sequences on Maize Pachytene Chromosomes by Fluorescence in situ Hybridization
Other Titles: 利用螢光原位雜交定位玉米中節與端粒序列於粗絲期染色體
Authors: 王中茹
Issue Date: Jun-2003
Publisher: 國立臺灣師範大學生命科學學系
Department of Life Science, NTNU
Abstract: 真核生物染色體的中節(centromere)區域色括一級收縮區(primary constriction)與環繞中節的異染色質(pericentric heterochromatin)。目前知道玉米中節的DNA是由中節特有的CentC重複性衛星DNA(satellite DNA)和逆轉移子(retrotransposon)以及其他多種重複性序列所組成。已有許多報告利用螢光原位雜交技術(fluorescence in situ hybridization, FISH)將這些中節序列定位在細胞有絲分裂中期(metaphase)染色體上,但由於這個時期染色體收縮得很短,螢光訊號的解析力低,故不易觀察這些DNA序列的精確位置。在本研究中,利用收縮程度小的減教分裂粗絲期染色體(pachytene chromosome)為螢光原位雜交標的,將CentC重複序列清楚定位於KYS及A344兩種玉米自交系的一級收縮區上,而非環繞中節的異染色質區域,且螢光訊號在十個粗絲期染色體中節的強度有所不同。由CentC訊號強度的差異可將中節區分為兩類,並發現與利用傳統aceto-carmine染色法所觀察到的兩種中節相互吻合。此外,以端粒序列(5’TTTAGGG-3’)n為探針,與兩種玉米自交系粗絲期染色體做原位雜交,由染色體末端所觀察到的訊號強弱差異,顯示端粒重複序列在兩種自交系中長度不同。另在KYS自交系中,第九條染色體短臂的端粒訊號位於末端異染色質節(knob)的內側,並非染色體的頂端。這可能是由於染色質(chromatin)高度纏繞(high-order folding)所造成的的結果。
The centromere region of eukaryotic chromosomes includes a primary constriction (centromere proper) and the pericentric heterochromatin. The DNA component of maize centromeres consists of centromere-specific CentC satellite repeats and retrotransposons, and a variety of other repetitive sequences. Fluorescence in situ hybridization (FISH) is a powerful tool for localizing repetitive sequences. Several reports presented the localizations of these centromeric sequences on metaphase chromosomes by FISH, but the precise locations of these sequences in centromeric regions could not be ascertained because of the low resolution of metaphase chromosomes. In this study, using meiotic pachytene chromosomes of two maize inbred lines, KYS and A344, as FISH targets, we demonstrated that the CentC element is present in the primary constriction but not in the pericentric heterochromatin. In addition, we observed differences in the strength of hybridization signals among the individual chromosomes in both inbred lines. The strength of signals could be classified into two typescorresponding to the appearance of centromeres based on aceto-carmine staining. Hybridization of pachytene chromosomes with the telomere repeat 5' -TTTAGGG-3' revealed the differences in length of telomeres between the two inbred lines. In KYS, the cluster of telomere signals was proximal to the terminal knob on 9S. This is interpreted to be an artifact resulting from high-order chromatin folding.
Other Identifiers: 748787BB-2CA8-09CC-DF7E-6DCF05C567D6
Appears in Collections:生物學報

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