On the Determination of Vascular Patterns During Tissue Differentiation in Excised Pea Roots

Torrey, John G.

doi:10.1002/j.1537-2197.1955.tb11110.x

Cited by 53 publications

(13 citation statements)

References 27 publications

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“…In dicot roots, there is a strong correlation between the size of the stele and the number of xylem poles, and the experimental manipulation of cell number in some dicot roots leads to variation in vascular pole number (Torrey, 1955). In Arabidopsis primary roots, the stele is usually comprised of 12-13 pericycle cells (Dolan et al, 1993) and 25-28 internal cells at stages when mature xylem and phloem elements are found (Dolan et al, 1993) (Fig.…”

Section: Research Articlementioning

confidence: 99%

Regulation of theArabidopsisroot vascular initial population byLONESOME HIGHWAY

2007

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Complex organisms consist of a multitude of cell types arranged in a precise spatial relation to each other. Arabidopsis roots generally exhibit radial tissue organization; however, within a tissue layer, cells are not identical. Specific vascular cell types are arranged in diametrically opposed longitudinal files that maximize the distance between them and create a bilaterally symmetric (diarch) root. Mutations in the LONESOME HIGHWAY (LHW) gene eliminate bilateral symmetry and reduce the number of cells in the center of the root, resulting in roots with only single xylem and phloem poles. LHW does not appear to be required for the creation of any specific cell type, but coordinately controls the number of all vascular cell types by regulating the size of the pool of cells from which they arise. We cloned LHW and found that it encodes a protein with weak sequence similarity to basic helix-loophelix (bHLH)-domain proteins. LHW is a transcriptional activator in vitro. In plants, LHW is nuclear-localized and is expressed in the root meristems, where we hypothesize it acts independently of other known root-patterning genes to promote the production of stele cells, but might also indirectly feed into established regulatory networks for the maintenance of the root meristem.

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Section: Research Articlementioning

confidence: 99%

Regulation of theArabidopsisroot vascular initial population byLONESOME HIGHWAY

2007

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“…Peas were used because they have developmentally wellcharacterized primary roots (Popham, 1955;Torrey, 1955;Rost et al, 1988). In an earlier investigation of pea root development that was done solely by the study of mitotic activity (Rost et al, 1988), pea root development could be explained by a process known as sector development (Rost, 1991).…”

Section: Developmentally Coordinated Sectors In Pea Root Developmentmentioning

confidence: 99%

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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“…Studies of this sort imply that the parameters heretofore measured need not alter for there to be a change in the vascular pattern within an individual root. Torrey (1955) attributed changes in pattern to "forces which control, either directly or indirectly, cell division and cell enlargement in the apical meristem." From numerous studies it is clear that components of the vascular tissue are already determined at distances of less than 100 pm from the root cap junction (Biinning 1951(Biinning , 1952Esau 1940;Heimsch 1951 ;Luxova and Lux 1974;Torrey 1955;Wilcox 1962~).…”

Section: Discussionmentioning

confidence: 97%

“…The investigations of Reinhard (1954) and tion in vascular pattern along the length of an Torrey (1955), which demonstrated that the root individual root (Hayward 1938;Heimsch 195 1 ; apex (the terminal 0.5 mm) controlled the initia Jost 1932;Meyer 1930;Miller 1958). Little at-tion and formation of vascular pattern in the tention, however, has been directed toward the elucidation of factors which might account for this variation.…”

Section: Introductionmentioning

confidence: 96%

The quiescent center and primary vascular tissue pattern formation in cultured roots of Zea

Feldman¹,

Torrey²

1975

Can. J. Bot.

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1975. The quiescent center and primary vascular tissue pattern formation in cultured roots of Zen. Can. J. Bot. 53: 2796-2803. Roots of Zea mays cv. Kelvedon 33 were cultured in nutrient media supplemented with varying concentrations of sucrose. In some instances an individual root was grown successively for periods of time in several different concentrations of sucrose. From this work it was shown that the complexity of the vascular patterns in cultured roots as well as the size of the quiescent center could be manipulated by altering the levels of sucrose in the nutrient medium. The simplest vascular patterns were found in roots in which the quiescent center was most reduced in size. In roots with relatively larger quiescent centers more complex vascular patterns were observed. Based on these studies a proposal is advanced concerning the relationship between the quiescent center and the initiation and maintenance of primary vascular tissue patterns in roots. FELDMAN, L. J., et J. G. TORREY. 1975. The quiescent center and primary vasculartissue pattern formation in cultured roots of Zea. Can. J. Bot. 53: 2796-2803.Des racines de Zea mays cv. Kelvedon 33 ont CtC cultivCes dans des milieux nutritifs additionnCs de diverses concentrations de sucrose. Dans quelques cas, une racine donnCe a Ct C cultivCe avec succes pendant plusieurs pCriodes successives dans plusieurs concentrations differentes de sucrose. A partir de ce travail, les auteurs montrent que la complexit6 des patrons vasculaires dans les racines cultivCes ainsi que la dimension du centre quiescent peuvent Ctre manipulees en modifiant le niveau de sucrose dans le milieu nutritif. Les patrons de vascularisation les plus simples se rencontrent dans les racines oC le centre quiescent est le plus petit. Des patrons de vascularisation plus complexes ont CtC obsewks dans les racines ayant un centre quiescent relativement plus gros. En se fondant sur ces Ctudes, les auteurs proposent une relation entre, d'une part, le centre quiescent et, d'autre part, I'initiation et la persistance des patrons du tissu vasculaire primaire dans les racines.[Traduit par le journal]

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On the Determination of Vascular Patterns During Tissue Differentiation in Excised Pea Roots

Cited by 53 publications

References 27 publications

Regulation of theArabidopsisroot vascular initial population byLONESOME HIGHWAY

Regulation of theArabidopsisroot vascular initial population byLONESOME HIGHWAY

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

The quiescent center and primary vascular tissue pattern formation in cultured roots of Zea

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