Genetic and Molecular Organization of Ribosomal DNA (Rdna) Variants in Wild and Cultivated Barley
AUTOR(ES)
Allard, R. W.
RESUMO
Twenty rDNA spacer-length variants (slvs) have been identified in barley. These slvs form a ladder in which each variant (with one exception) differs from its immediate neighbors by a 115-bp subrepeat. The 20 slvs are organized in two families, one forming an eight-step ladder (slvs 100-107) in the nucleolus organizer region (NOR) of chromosome 7 and the other a 12-step ladder (slvs 108a-118) in the NOR of chromosome 6. The eight shorter slvs (100-107) segregate and serve as markers of eight alleles of Mendelian locus Rrn2 and the 12 longer slvs (108a-118) segregate and serve as markers of 12 alleles of Mendelian locus Rrn1. Most barley plants (90%) are homozygous for two alleles, including one from each the 100-107 and the 108a-118 series. Two types of departures from this typical pattern of molecular and genetic organization were identified, one featuring compound alleles marked by two slvs of Rrn1 or of Rrn2, and the other featuring presence in Rrn1 of alleles normally found in Rrn2, and vice versa. The individual and joint effects on adaptedness of the rDNA alleles are discussed. It was concluded that selection acting on specific genotypes plays a major role in molding the strikingly different allelic and genotypic frequency distributions seen in populations of wild and cultivated barley from different ecogeographical regions.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=1204228Documentos Relacionados
- Genetic diversity and ecogeographical differentiation among ribosomal DNA alleles in wild and cultivated barley.
- Characterization of ribosomal DNA (rDNA) in Drosophila arizonae
- Evolution of Ribosomal DNA (Rdna) Genetic Structure in Colonial Californian Populations of Avena Barbata
- Transcription Factor UAF, Expansion and Contraction of Ribosomal DNA (rDNA) Repeats, and RNA Polymerase Switch in Transcription of Yeast rDNA
- Identification of the Bacterial Community of Maple Sap by Using Amplified Ribosomal DNA (rDNA) Restriction Analysis and rDNA Sequencing