Intraspecific variation of nuclear DNA content in plant species

Abstract

SUMMARY-In recent years, wide DNA changes have been described among and within plant species. As to intraspecific DNA variations, they have been reported in a number of species, namely, Linum usitatissimum, Microseris douglasii, M. bigelovii, Zea mays, Helianthus annuus and others. DNA changes have been detected mostly by Feulgen cytophometry, that, if experiments follow some general rules, may be adequate for quantitative analyses. Biochemical analyses have, in some cases, confirmed the cytophotometric findings; it is generally accepted that DNA variations involve loss or increase of repeated DNA sequences (including rDNA). Concerning the origin and inheritance of DNA changes, a marked deviation from normal segregation rates are found in different species, and genome size seems to change following precise mechanisms. The functional significance of DNA changes is discussed: in many (but not all) cases a relationship has been established between DNA changes and adaptation to different environments, through nucleotypic effects. These aspects are summarized with particular reference to intraspecific DNA variations in the sunflower, which occur in cultivated varieties, hybrids and inbred lines within a single generation.

Genome size and plant development in hexaploid Festuca arundinacea

“…The generation time is correlated positively with the genome size in F. arundinacea (Fig. 8) and H. annuus, of plants (reviewed by Cavallini & Natali, 1991; while no such correlation exists in P. sativum (cf. data Cavallini eta!., 1993;Natali etal., 1993). presented here with that of Natali et al, 1993 and We suggest that these changes in development are Cavallini et al, 1993).…”

“…These results may be added to several others to be found in the literature to the effect that intraspecific changes in the basic amount of nuclear DNA do occur (reviewed by Bennett, 1985;Cavallini & Natali, 1991), due to the presence in the genome, possibly more commonly in plants than in animals, of fluid domains. These fractions of nuclear DNA, made up mostly of repeated sequences, are capable of rapid quantitative changes in response to developmental and/or environmental stimuli (reviewed by Cionini, 1989;Bassi, 1990;Cullis, 1990;Nagl, 1990).…”

“…In the same way as in other species (cf. Cullis, 1990;Cavallini & Natali, 1991), these changes are linked to variations in the amount of heterochromatin and in the frequency of repeated DNA sequences, and particularly of a fraction of them (the 'fluid' domains).…”

Nuclear DNA variability within Pisum sativum (Leguminosae): nucleotypic effects on plant growth

“…Quantitative nuclear DNA intraspecific variation has been described in a number of species, such as Linum usitatissimum, Microseris douglasii, M. bigelovii, Zea mays, Helianthus annuus and others (see Cavallini & Natali, 1991). Changes in nuclear DNA content, excluding chromosome endoreduplication and polyploidization, may affect the relative proportions of DNA families in the genome.…”

“…In complex multicellular vascular plants, nucleotypic effects may be additive at subsequent cell cycles, so affecting many characters such as growth rate and habit, and generation time (Bennett, 1985;1987). Following this hypothesis, nucleotypic effects should be very important in ecological adaptation of plants, with significant correlations between low DNA contents and adaptation to stressful environments (Cavallini & Natali, 1991, and references therein). However, a direct correlation between quantitative DNA variation and growth rate has not yet been fully established.…”