Heterosis for H1 histone content in aging Drosophila hybrids.

Temporal changes in electrophoretically separated histones were investigated in a heterotic and a non-heterotic Drosophila melanogaster F1 hybrid and in their respective inbred parents. Histones were acid-extracted from isolated nuclei of larvae and of adult flies at selected age intervals. Five major histone fractions were identified, and distinct quantitative differences in H1 histones were found between early third instar larvae and adults. Age-related quantitative histone differences were also apparent when hybrids were compared with parents. Heterotic hybrids maintained a significantly higher proportion of H1 histone fractions with aging than did all parents or non-heterotic hybrids. Relative H1 histone quantity in non-heterotic hybrids paralleled the decline observed in parents. These data suggest a relation between the manifestation of hybrid vigor and the maintenance of chromatin structure during the aging process.