Placement of genes for ribosomal RNA within the nucleolar organizing body of Zea mays

Doerschug, Earle B.

doi:10.1007/bf00288326

Cited by 28 publications

(4 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…McClinrock (1934) concluded that the heterochromatic region alone was the NOR, while AnastassovaKristeva et al (1977) suggested that it was the secondary constriction alone. However, several other workers (Givens & Phillips, 1976;Doerschug, 1976;and Subrahmanyam & Azad, 1978 a, b) concluded that the expression and size of the secondary constriction would be a reflection of the extent of dispersion of rDNA coincident with the organisation of a nucleolus. I n Hordeum vulgare, it was conclusively demonstrated that the achromatic gap (secondary constriction) only represents the degree of activity through the dispersion of rDNA and not the 'sole site' for rDNA (Subrahmanyam & Azad, 1978 a).…”

mentioning

confidence: 99%

Nucleolar number variation in Hordeum species, their haploids and interspecific hybrids

Jessop

Subrahmanyam

1984

Genetica

View full text Add to dashboard Cite

Nucleolar number variation has been investigated in root tip cells by cytologically determining the number of nucleoli per cell in autoploids and alloploids of Hordeum species, their haploids and intcrspecific hybrids. The nucleolus organisers in autoploid types of H. vulgare or H. bulbosum did not show any alterations irrcspective of the ploidy level. The nucleolar number variation in these species results from a definite pattern of fusion and the maximum number of nucleoli per nucleus corresponds to the number of secondary constrictions. Nucleolus formation in alloploids and interspecific hybrids is impaired on some of the NORs, suggesting differential amphiplasty or nucleolar dominance. A comparison of nucleolar formation in the alloploid species (brachyantherum, arizonicum, procerum and parodii), their haploids, and the interspecific hybrids revealed different degrees of variation from the expected mean and maximum numbers of nucleoli. While the deviations in hybrids between alloploids (H. arizonicum and H. brachyantherum or H. procerum and H. brachyantherum) are marginal, nucleolar dominance is more pronounced in hybrids involving H. vulgare or H. bulbosum as one of the parents and is invariably associated with the disappearance of the secondary constriction(s) from the NOR(s) contributed by one of the parents, and the number of nucleoli is appropriately reduced.

show abstract

mentioning

confidence: 99%

Nucleolar number variation in Hordeum species, their haploids and interspecific hybrids

Jessop

Subrahmanyam

1984

Genetica

View full text Add to dashboard Cite

show abstract

“…A great number of cytogenetic studies have been carried out on Z. mays [16,25,26,44,50,51]. These have shown that the NOR is composed of the secondary constriction (SC) and the adjacent heterochromatic knob (Fig.…”

Section: Relationship Between the Nucleolonema And The Nor-bearing Chmentioning

confidence: 99%

“…Zea mays presents some advantages since previous cytogenetic studies have shown that, in this species, there is only one pair of NORs located in chromosome 6. Each NOR consists of the secondary constriction and adjacent heterochromatic knob [16,25,26,44,50,51]. The 2 NORs are located in the same nucleolus in > 90°/0 of the radicle cells [55].…”

Section: Introductionmentioning

confidence: 99%

Three‐dimensional electron microscopy of the nucleolus and nucleolus‐associated chromatin (NAC) during early germination of Zea mays L.

Motté

Deltour

Mosen

et al. 1988

Biology of the Cell

View full text Add to dashboard Cite

Nucleoli and nucleolus‐associated chromatin (NAC) of radicle cells have been three‐dimensionally reconstructed from serial ultrathin sections during early germination of Zea mays. As a preliminary, the effect of 5 methods of fixation on the ultrastructure of the active NAC were tested qualitatively and quantitatively. It appeared that paraformaldehyde best preserved the fibrillar centres (FCs) and was consequently used for the 3‐D reconstructions. In quiescent cells, the NAC forms either 2 short internal strands about 0.7 μm thick running within the nucleolus or 2 peripheral knobs of the same diameter. Whatever its morphology, the NAC was composed of one clear zone, i.e., secondary constriction (SC) of the nucleolar organizer region (NOR), and one electron‐opaque zone, i.e., heterochromatic segment (HS). During germination the NAC was always connected to the nuclear envelope (NE) by a bridge of dense chromatin. The NAC strands or knobs of the quiescent cells are likely to be the counterpart of the 2 NORs of this species. 10–12 hr after onset of germination, one or several networks of nucleolar vacuoles were formed within which the whole NAC was located. Chromatin fibers about 12 nm thick emerged from unfolding portions of the NAC within these “nucleolar chromatin dispersal vacuoles” (NCDV). At 24 hr, the NAC appeared as 2 dichotomous strands. Seventy‐two hr after germination both the stretching out and branching of the NAC were more pronounced. After 120 hr, the transcribing ribosomal genes for each NAC strand together with the newly synthesized RNP transcripts formed a layer of dense fibrillar component surrounding a thin axis which was composed mainly of pale material. Together these formed a typical plant nucleolonema.

show abstract

“…Nucleologenesis has been shown to depend on the resumption of transcription of genes coding for rRNA (Gim6nez-Martfn et al, 1974), genes which are clustered in the chromosomal segment known as the nucleolar organizer region (NOR) (Phillips et al, 1971Givens & Phillips, 1976;Ramfrez & Sinclair, 1975;Doerschug, 1976). Dissolution occurs during prophase.…”

Section: Introductionmentioning

confidence: 99%

Nucleologenesis and number of ribosomal RNA genes in maize

Torre¹,

Colinas²

1978

Genetica

View full text Add to dashboard Cite

Placement of genes for ribosomal RNA within the nucleolar organizing body of Zea mays

Cited by 28 publications

References 37 publications

Nucleolar number variation in Hordeum species, their haploids and interspecific hybrids

Nucleolar number variation in Hordeum species, their haploids and interspecific hybrids

Three‐dimensional electron microscopy of the nucleolus and nucleolus‐associated chromatin (NAC) during early germination of Zea mays L.

Nucleologenesis and number of ribosomal RNA genes in maize

Contact Info

Product

Resources

About