The fate of ribosomal genes in three interspecific somatic hybrids of Medicago sativa: Three different outcomes including the rapid amplification of new spacer-length variants

被引:29
作者
Cluster, PD [1 ]
Calderini, O [1 ]
Pupilli, F [1 ]
Crea, F [1 ]
Damiani, F [1 ]
Arcioni, S [1 ]
机构
[1] CNR, IST RIC MIGLIORAMENTO GENET PIANTE FORAGGERE, I-06128 PERUGIA, ITALY
关键词
alfalfa rDNA; fluorescent in situ hybridization; rDNA IGS variation; somaclonal variation; unequal recombination;
D O I
10.1007/BF00224079
中图分类号
S3 [农学(农艺学)];
学科分类号
0901 ;
摘要
We have characterized the genetic consequences of somatic hybridization within the ribosomal DNA (rDNA) of three interspecific hybrids, each involving M. sativa as one of the parents. Restriction-fragment-length-polymorphisms (RFLPs) of rDNA spacers and fluorescent-in-situ-hybridization (FISH) of an 18S-gene probe to mitotic chromosomes were used to compare parental and hybrid species. The M. sativa-coerulea hybrid retained all six parental nucleolar-organizing regions (NORs) and all parental RFLPs representing a complete integration of rDNA. The M. sativa-arborea hybrid retained five of six parental NORs while losing half of the arborea-specific RFLPs, indicating that simple chromosome loss of one arborea NOR accounted for the RFLP losses. Dramatic alterations occurred within the M. sativa-falcata hybrid where five of six parental NORs were retained and new rDNA RFLPs were created and amplified differentially among somaclonal-variant plants. The molecular basis of the new RFLPs involved increased numbers of a 340-bp subrepeating element within the rDNA intergenic spacer (IGS), suggesting that recurrent cycles of unequal recombination occurred at high frequency within the rDNA in somatic lineages.
引用
收藏
页码:801 / 808
页数:8
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