REDUNDANCY MODULATION OF NUCLEAR-DNA SEQUENCES IN DASYPYRUM-VILLOSUM

In order to assess fluid domains in the genome of Dasypyrum villosum, Feulgen/DNA cytophotometric determinations and molecular and cytologic al DNA-DNA hybridization experiments were carried out in resting embry os and developing seedlings from yellow and brown caryopses belonging to different populations. The cytophotometric data showed that the bas ic amount of nuclear DNA is, on average, 12% higher in 2-day-old seedl ings from yellow caryopses as compared to those from brown caryopses. It increases in each individual during seed germination, to a higher e xtent in seedlings from yellow caryopses than in those from brown cary opses. DNA content also differs up to 13% between plants within a cary opsis-colour group and up to 40% between populations. Dot-blot hybridi zation of a 396-bp D. villosum-specific DNA repeat to genomic DNA extr acted fi-om embryos in dry seeds, or from seedlings belonging to singl e progenies of plants from different populations, confirmed the cytoph otometric results. The redundancy in the genome of sequences hybridizi ng to the 396-bp element differs significantly both between population s and between plant progenies within a population. During seed germina tion these sequences are the more amplified the less they are redundan t in the genome of resting embryos, and amplification occurs to a sign ificantly-greater extent in seedlings from yellow caryopses than in th ose from brown caryopses. H-3-labelled 396-bp sequences hybridize at o r near the telomeres of most chromsome pairs though only to the shorte r of the two subtelocentric pairs. The hybridization level is higher i n seedlings from yellow caryopses that in those from brown caryopses, and a linear correlation exists between the number of silver grains co unted over the labelled regions of each chromosome pair in the two gro ups of seedlings. Possible control mechanisms of the observed changes in the nuclear genome, and the role of these changes in developmental regulation and environmental adaptation, are discussed.