Isolation and characterization of genome-specific DNA sequences in Triticeae species.
Two contrasting genome-specific DNA sequences were isolated from Aegilops speltoides (wild goat grass) and Hordeum chilense (wild barley), each representing more than 1% of the genomes. These repetitive DNA fragments were identified as being genome-specific before cloning by genomic Southern hybridization (using total genomic DNA as a probe), and hence extensive screening of clones was not required. For each fragment, up to six recombinant plasmid clones were screened and about half were genome-specific. Clone pAesKB52 from Ae. speltoides was a 763 bp EcoRI fragment, physically organized in simple tandem repeats and shown to localize to sub-telomeric chromosome regions of species with the Triticeae S-genome by in situ hybridization to chromosomes. The sequence data showed an internal duplication of some 280 bp, which presumably occurred before sequence amplification and dispersion, perhaps by unequal crossing-over or reciprocal translocation. In situ hybridization showed that the sequence distribution varied between closely related (S-genome) species. Clone pHcKB6 was a 339 bp DraI fragment from H. chilense, also tandemly repeated but more variable; loss of the DraI site resulting in a ladder pattern in Southern blots which had little background smear. In situ hybridization showed that the tandem repeats were present as small clusters dispersed along all chromosome arms except at a few discrete regions including the centromeres and telomeres. The clone hybridized essentially specifically to the H-genome of H. chilense and hence was able to identify the origin of chromosomes in a H. chilense x Secale africanum hybrid by in situ hybridization.(ABSTRACT TRUNCATED AT 250 WORDS)
Anamthawat-Jónsson
K
K
Department of Cell Biology, John Innes Centre for Plant Science Research, Norwich, UK.
Heslop-Harrison
J S
JS
D001483:Base Sequence; D005075:Biological Evolution; D015139:Blotting, Southern; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics / Q000302:isolation & purification*; D016678:Genome; D017404:In Situ Hybridization, Fluorescence; D008969:Molecular Sequence Data; D006109:Poaceae / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid
D004247:DNA