Experimental control of the activity of the quiescent centre in excised root tips of Zea mays

Webster, Peter L.; Langenauer, Haviva D.

doi:10.1007/bf00388580

Cited by 49 publications

(18 citation statements)

References 20 publications

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“…The second approach demonstrated that inhibition of DNA synthesis lowered steady-state levels of H2A mRNA and showed that its expression was replication dependent. Furthermore, we could not detect any expression of H2A mRNA in the root quiescent center, which is known for its very slow cell division rates in all angiosperm roots studied (Webster and Langenauer, 1973;Clowes, 1975), nor in noncycling, mature root tissues. This could not be attributed to the lack of sensitivity to H2A mRNA, since low to moderate levels of mRNA are detectable by standard colorimetric techniques used with the DIG-labeling protocol (Kiyama et al, 1990;Tanimoto and Rost, 1993).…”

Section: Replication-dependent Expression Of H2a Mrnamentioning

confidence: 75%

DNA Replication-Dependent Histone H2A mRNA Expression in Pea Root Tips

1993

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Histone H2A mRNA is selectively expressed in scattered subpopulations of cells in the pea (Pisum sativum) root apical meristem. To study whether this specific expression was associated with the cell cycle, a double-labeling technique was used to identify cells replicating DNA during S phase and those expressing H2A mRNA. Cells in S phase were detected by rH]thymidine incorporation and autoradiography, whereas cells containing H2A mRNA were identified by in situ hybridization using digoxigenin-labeled probes. Approximately 92% of the [3H]thymidine-labeled S-phase cells expressed H2A mRNA and 85% of cells that expressed H2A mRNA were in S phase. In root tissue located basal to the promeristem, synchronous co-located expression was observed in scattered packets of proliferating cells. Furthermore, neither H2A mRNA nor Sphase cells could be detected within the quiescent center or mature root cap. When DNA synthesis was inhibited with hydroxyurea, a commensurate and specific decrease in steady-state levels of H2A mRNA was found. We concludethat cell-specific expression of pea histone H2A mRNA is replication dependent and that H2A mRNA is transiently accumulated during a period of the cell cycle that mostly overlaps the S phase. We propose that the overlap between H2A expression and S phase could occur if H2A mRNA accumulation began in late G1 and abated in late S.Histone proteins are required for the packaging of eukaryotic DNA into chromatin and can be divided in three groups based on their characteristic modes of expression (Schiimperli, 1986). The largest group is cell-cycle-regulated and exhibits expression that is dependent on DNA replication. The second group, consisting of replacement variants, exhibits replication-independent expression and is expressed in nondividing cells of mature tissues. A third minor group, consisting of tissue-specific variants, is expressed in a replication-independent manner in unique tissues such as reproductive organs. Differences in genomic organization and gene structure mark each group. The regulation of replicationdependent histone expression has been extensively studied and reviewed (Hereford et al.,

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Section: Replication-dependent Expression Of H2a Mrnamentioning

confidence: 75%

DNA Replication-Dependent Histone H2A mRNA Expression in Pea Root Tips

1993

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“…In both plants fast cycling cells exist side by side with non-cycling cells in the stele and slow cycling cells exist with non-cycling cells in the quiescent centre, but DNA builds up in at least some of the stelar cells after cycling has ended. There is no evidence from either plant grown in this laboratory for the cycling cells of the quiescent centre being confined to a particular sub-region as Webster and Langenauer (1973) reported for another cultivar of Zea.…”

Section: Discussionmentioning

confidence: 52%

TEMPERATURE AND THE COORDINATION OF CELL CYCLES WITHIN THE ROOT MERISTEM OF ALLIUM SATIVUM L.

Taylor

Clowes

1978

New Phytologist

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SUMMARYCell cycling has been surveyed throughout the meristem over a range of temperature by stathmokinetic and DNA-labelling methods.There is a quiescent centre of ninety cells either out of cycle or with prolonged cycles. The cap initials have the highest rate of cell production, but only over a short temperature range. Outside that range the distal stelar cells have higher rates. The numbers of cells in the cap and its initials fall off with increasing temperature and there is a twelve-fold variation in the rate at which the initials can refurnish the cap with new cells. The reduction in cell production that occurs towards the proximal margin of the meristem is due solely to lowering the growth fraction and the meristem contracts at high temperatures.The phases of the cycle as fractions of the whole vary from region to region and with temperature in the same region. Gl is the most variable phase though it is never eliminated as it is in Zea and the shortening of the mean cycle of cycling cells in the stele from the tip to the proximal margin of its meristem is brought about largely by the reduction of Gl and, to a lesser extent, of G2 while both S and M lengthen. S and M decrease as the temperature increases from 20 to 30°C while Gl and G2 are minimal at 25°C. The coordination of cycle parameters inAllium is discussed in relation to the anatomical features of its meristem and contrasted with that in Zea.

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“…It has been determined that cells of the root quiescent centre can be induced to undergo greatly increased DNA synthesis and mitotic activity by treatments which arrest growth and subsequently allow it to proceed (Clowes and Stewart 1967;Webster and Langenauer 1973;Langenauer et al 1974). The work that bears most directly upon the present investigation is that of Clowes and Stewart (1967) in which young seedlings of Zea mays were put into a dormant state by exposure to low temperature and subsequently were restored to active growth by a return to normal temperature.…”

Section: Discussionmentioning

confidence: 93%

“…Clowes and Stewart (1967) have reported activity in the quiescent centre of seedling roots of Zea after a cold-induced period of dormancy. Finally, it has been shown that in cultured roots in which cell proliferation in the meristem has been arrested by carbohydrate starvation, DNA synthesis occurs in the quiescent centre when carbohydrate is added to the culture medium (Webster and Langenauer 1973;Langenauer et al 1974).…”

Section: Introductionmentioning

confidence: 99%

Developmental studies on Euphorbia esula: seasonal variation in the apices of long roots

Raju¹,

Steeves²,

Maze³

1976

Can. J. Bot.

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Abstract:Long-root apices of Euphorbia esula L. were supplied with [ 3 H]thymidine in the field on 11 occasions during the growing season. Autoradiographs of the root apices showed that the characteristic quiescent centre of long roots was absent in a large percentage of the roots in the early part of the growing season. It is suggested that the cells of the quiescent centre play an important role in the seasonal reactivation of the perennial roots of this species.

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Experimental control of the activity of the quiescent centre in excised root tips of Zea mays

Cited by 49 publications

References 20 publications

DNA Replication-Dependent Histone H2A mRNA Expression in Pea Root Tips

DNA Replication-Dependent Histone H2A mRNA Expression in Pea Root Tips

TEMPERATURE AND THE COORDINATION OF CELL CYCLES WITHIN THE ROOT MERISTEM OF ALLIUM SATIVUM L.

Developmental studies on Euphorbia esula: seasonal variation in the apices of long roots

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