REPEATED DNA-SEQUENCES ISOLATED BY MICRODISSECTION .1. KARYOTYPING OFBARLEY (HORDEUM-VULGARE L)

We report on microdissection, cloning and sequence, and Southern and f luorescence in situ hybridization (FISH) analysis of one moderately an d one highly amplified repetitive DNA element, pHvMWG2314 and pHvMWG23 15, respectively, isolated from barley (Hordeum vulgare L.) chromosome arm 3HL. The pHvMWG2315 sequence hybridizes to all 14 telomeric or su btelomeric regions of the barley chromosomes as determined by FISH. Th e 50 different hybridization sites that include intercalary signals al low the discrimination of all 14 chromosome arms and the construction of a karyotype of barley. The tandemly repeated subtelomeric element o f 331 bp exists in all Triticeae species tested (H. vulgare, Agropyron elongatum, Secale cereale, Triticum tauschii, T. turgidum, and T. aes tivum). It is AT rich (66%), exhibits 84% sequence homology to subfrag ments of the D genome ''specific'' 1-kb element pAs1 of T. tauschii an d 75% homology to the interspersed genome-specific DNA sequence pHcKB6 from H. chilense. The repetitive sequence pHvMWG2314 is moderately am plified in barley and highly amplified in hexaploid wheat. The in situ experiments revealed no distinct signals on barley chromosomes, indic ating a dispersed character for the sequence. The significance of the results for the identification of chromosomes and chromosome aberratio ns in FISH experiments are discussed.