Variations in 5S rDNAs in diploid and tetraploid offspring of red crucian carp × common carp.-猫眼课题宝

红鲫×鲤鱼二倍体和四倍体后代5S rDNA的变异

DOI：

10.1186/s12863-017-0542-2

发表时间：

2017-08-08

期刊：

BMC genetics

影响因子：

2.9

通讯作者：

中科院分区：

生物学3区

文献类型：

作者：

Ye L;Zhang C;Tang X;Chen Y;Liu S

来源链接：

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5549377/

异源四倍体杂交鱼(4nAT)是利用红鲤(Carassius auratus red var.，♀)与鲤鱼(Cyprinus Carpio L.，♂)属间杂交获得的异源四倍体杂交鱼，为研究杂交和多倍化对5S rDNA进化的影响提供了一个很好的平台。父本鲤鱼的5S rDNA由编码序列(CDS)和非转录间隔区(NTS)单位组成，而母本红鲤的5S rDNA由CDS和NTS单位组成，也含有数量可变的插入区(IPRs)。两种亲本鱼类的5S rDNA的CDSS序列都是保守的，而它们的NTS单元似乎经历了快速进化。二倍体杂交种2nF1的5S rDNA在两个亲本中均有遗传，经测序分析，2nF1的5S rDNA没有同源重组的迹象。通过细菌人工染色体(BAC)测序，从异源四倍体后代4nAT中获得了两个5S rDNA片段，全长16,457bp。将该序列与从4nAT基因组DNA中扩增出的5S rDNA序列相结合，推测4nAT的5S rDNA可能遗传自母本红鲤。此外，4nAT的5S rDNA中的IPR含有A-重复序列和TA-重复序列，而2nF1的5S rDNA中的IPR则不是这样。我们还利用荧光原位杂交技术(FISH)在亲本后代和杂交后代的染色体上检测到了5S rDNA的200个核苷酸片段的两个信号。推测在不同倍性杂交鱼的5S rDNA进化过程中，多倍化过程中可能发生了位点间基因转换事件和串联重复插入事件。本研究为揭示5S rDNA进化与杂交、多倍化之间的关系提供了新的思路，对阐明多倍体鱼类基因组进化具有重要意义。

The allotetraploid hybrid fish (4nAT) that was created in a previous study through an intergeneric cross between red crucian carp (Carassius auratus red var., ♀) and common carp (Cyprinus carpio L., ♂) provided an excellent platform to investigate the effect of hybridization and polyploidization on the evolution of 5S rDNA. The 5S rDNAs of paternal common carp were made up of a coding sequence (CDS) and a non-transcribed spacer (NTS) unit, and while the 5S rDNAs of maternal red crucian carp contained a CDS and a NTS unit, they also contained a variable number of interposed regions (IPRs). The CDSs of the 5S rDNAs in both parental fishes were conserved, while their NTS units seemed to have been subjected to rapid evolution. The diploid hybrid 2nF1 inherited all the types of 5S rDNAs in both progenitors and there were no signs of homeologous recombination in the 5S rDNAs of 2nF1 by sequencing of PCR products. We obtained two segments of 5S rDNA with a total length of 16,457 bp from allotetraploid offspring 4nAT through bacterial artificial chromosome (BAC) sequencing. Using this sequence together with the 5S rDNA sequences amplified from the genomic DNA of 4nAT, we deduced that the 5S rDNAs of 4nAT might be inherited from the maternal progenitor red crucian carp. Additionally, the IPRs in the 5S rDNAs of 4nAT contained A-repeats and TA-repeats, which was not the case for the IPRs in the 5S rDNAs of 2nF1. We also detected two signals of a 200-bp fragment of 5S rDNA in the chromosomes of parental progenitors and hybrid progenies by fluorescence in situ hybridization (FISH). We deduced that during the evolution of 5S rDNAs in different ploidy hybrid fishes, interlocus gene conversion events and tandem repeat insertion events might occurred in the process of polyploidization. This study provided new insights into the relationship among the evolution of 5S rDNAs, hybridization and polyploidization, which were significant in clarifying the genome evolution of polyploid fish.