Variation in the ribosomal RNA genes among individuals of Vicia faba

Abstract

Length heterogeneity in the ribosomal repeat of Vicia faba is due to the presence of variable numbers of a 325 bp subrepetitive element within the nontranscribed spacer region. The distribution of size classes among 88 individuals within a population was investigated by blot-hybridization. We find that individual plants can exhibit more than 20 size classes and that hybridization patterns are highly diverse from individual to individual, more so than for any species so far investigated. In contrast, no such differences are observed in patterns for different tissues from a single plant or from parental to F1 generation. Some changes were observed in the F2 generation. We conclude that unequal recombination can give rise to the diversity that we observe for the V. faba rDNA repeats.

Characterization of Satellite DNA from Three Marine Dinoflagellates (Dinophyceae): Glenodinium sp. and Two Members of the Toxic Genus, Protogonyaulax

“…In recent years, Hoechst dye 33528, which binds preferentially to A-T3 rich regions of DNA, has become increasingly useful in resolving cp-and mtDNA from nDNA in algae (1,14,19) and terrestrial plants (25). Organelle DNA species frequently migrate as low density satellite bands above the main nuclear DNA band in the Hoechst dye-CsCl gradients.…”

“…These Hoechst dye-CsCl gradients have also been exploited in the separation of terrestrial plant nuclear ribosomal DNA from total cellular DNA. Ribosomal DNA frequently appears as a high density satellite band below the nDNA in these gradients (25).…”

Ribosomal DNA variation among populations of a Pinus rigida Mill. (pitch pine) ecosystem: I. Distribution of copy numbers

“…For example, Rogers & Bendich (1987) reported a 12-fold variation within individuals, but almost a 95-fold difference among individuals within a population of Vicia faba. In maize, Buescher et al, (1984), reported a 4.6-fold difference among individuals; while Zhang et al, (1990) found a 6.4-fold difference among individuals The dwarf nature of these populations has been described as an apparent adaptation to higher fire frequencies relative to the other parts of the Pine Barrens, as well as to the distribution range of pitch pine (Ledig & Fryer, 1973;Good & Good, 1975;Givnish, 1981).…”

“…Therefore, no conclusion can be drawn about, (a) intra-individual variation for copy numbers, (b) absolute maximum and minimum number of copies among individuals in any given population, and (c) if there are dines (smooth vs. stepped; Endler, 1977) for copy numbers between populations in relation to environmental gradients. Variation for rRNA genes within individuals has been reported in organisms such as Drosophila (Tartoff, 1975), Neurospora (Russell & Rodland, 1986) and Vicia (Rogers & Bendich, 1987). Pitch pine is known to sprout by means of epicormic buds (buds under bark) following fire.…”

“…Although the function and maintenance of a majority of these sequences is obscure, the product of one of them, the ribosomal RNA (rRNA), plays a central role in protein synthesis, and hence is important in growth, development and reproduction (Stern et a!., 1989). Ribosomal DNA (rDNA) consists of a tandem array of repeat units varying from 500 to 40,000 copies per genome (Long & Dawid, 1980;Rogers & Bendich, 1987).…”