Cytogenetic evidence of nucleolar dominance in allotetraploid species of Brachypodium
Cytogenetic evidence of nucleolar dominance in allotetraploid species of Brachypodium
复制标题
DOI：
10.1139/g08-017
复制
发表时间：
2008-05-01
期刊：
影响因子：
3.1
通讯作者：
Hasterok, Robert
中科院分区：
文献类型：
--
作者：
Idziak, Dominika;Hasterok, Robert
采用序列银染色和荧光原位杂交（FISH）技术，对6种异源四倍体（2n = 4x = 30）短茅及其推测祖先B. distachyon （2n = 2x = 10）和ABR114 （2n = 2x = 20）的分生根尖细胞45S rDNA位点的活性和数量进行了测定。利用abr114或ABR1-63-E6 BAC克隆的总核DNA作为辅助探针，可以通过FISH区分构成异源四倍体短柄植物物种生态型的两个基因组，并明确确定显性和抑制rRNA基因的亲本关系。每个二倍体物种都有两个rDNA位点，都具有转录活性。同种异体四倍体短柄植物6个生态型的45S rDNA位点数始终等于其假定的二倍体亲本的位点数之和。两个较小的位点位于ABR114染色体组对应的染色体上，两个较大的位点位于双歧杆菌起源的染色体上。在所有的异源四倍体生态型中，只有B. distachyon-like基因组的rRNA基因具有转录活性，而来自其他亲本基因组的rDNA基因总是被抑制。因此，首次证实了短茅属同种异体四倍体（2n = 4x = 30）存在核仁优势。
Sequential silver staining and fluorescence in situ hybridization (FISH) were used to establish activity and number of 45S rDNA sites in meristematic root tip cells of 6 ecotypes of allotetraploid (2n = 4x = 30) species of Brachypodium and their putative ancestors, B. distachyon (2n = 2x = 10) and ABR114 (2n = 2x = 20). Using either total nuclear DNA of ABR 114 or the ABR1-63-E6 BAC clone from a B. distachyon genomic library as an auxiliary probe, it was possible to distinguish by FISH between the two genomes composing the ecotypes of allotetraploid Brachypodium species and to determine unambiguously the parentage of both dominant and suppressed rRNA genes. Each of the diploid species possessed two rDNA loci, both transcriptionally active. The number of 45S rDNA sites in 6 ecotypes of allotetraploid Brachypodium species was always equal to the sum of loci present in their putative diploid parents. Two smaller sites were located in chromosomes corresponding to the ABR114 chromosomal set, and two larger ones in the chromosomes of B. distachyon origin. In all analyzed allotetraploid ecotypes, only rRNA genes belonging to the B. distachyon-like genome were transcriptionally active, while rDNA from the other parental genome was always suppressed. Thus the occurrence of nucleolar dominance in the allotetraploid (2n = 4x = 30) species of Brachypodium is demonstrated for the first time.