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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK; Malden, USA : Munksgaard International Publishers
    Physiologia plantarum 123 (2005), S. 0 
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The plant hormone auxin plays a crucial role in the upstream regulation of many processes, making the study of its action particularly interesting to understand plant development. In this review we will focus on the effects auxin exerts on cell cycle progression, more specifically, during the initiation of lateral roots. Auxin fulfils a dominant role in the initiation of a new lateral root primordium. How this occurs remains largely unknown. Here we try to integrate the classical auxin signalling mechanisms into recent findings on cell cycle regulation. How both signalling cascades are integrated appears to be complex and is far from understood. As a means to solve this problem we suggest the use of a lateral root-inducible system that allows investigation of the early signalling cascades initiated by auxin and leading to cell cycle activation.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2048
    Keywords: Key words:Arabidopsis (cell cycle) ; CKS1At expression ; Endoreduplication ; Meristem ; Mitotic cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Although endoreduplication is common in plants, little is known about the mechanisms regulating this process. Here, we report the patterns of endoreduplication at the cellular level in the shoot apex of Arabidopsis thaliana L. Heynh. plants grown under short-day conditions. We show that polyploidy is developmentally established in the pith, maturing leaves, and stipules. To investigate the role of the cell cycle genes CDC2aAt, CDC2bAt, CYCB1;1, and CKS1At in the process of endoreduplication, in-situ hybridizations were performed on the vegetative shoot apices. Expression of CDC2aAt, CDC2bAt, and CYCB1;1 was restricted to mitotically dividing cells. In contrast, CKS1At expression was present in both mitotic and endoreduplicating tissues. Our data indicate that CDC2aAt, CDC2bAt, and CYCB1;1 only operate during mitotic divisions, whereas CKS1At may play a role in both the mitotic and endoreduplication cycle.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2048
    Keywords: Key words:Arabidopsis (cyclin) ; Cell cycle ; D-type cyclin ; Lateral root primordia formation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. D-type cyclins are believed to regulate the onset of cell division upon mitogenic signaling. Here, the isolation is reported of a new D-type cyclin gene (CYCD4;1) of Arabidopsis thaliana (L.) Heynh. during a two-hybrid screen using the cyclin-dependent kinase CDC2aAt as bait. Transcription of CYCD4;1 can be induced by sucrose. The co-regulated expression of CYCD4;1 and CDC2aAt in starved suspension cultures upon mitogenic stimulation indicates that the formation of a complex between these two partners is important for the resumption of cell division activity. By in-situ hybridizations CYCD4;1 was shown to be expressed during vascular tissue development, embryogenesis, and formation of lateral root primordia. Expression during the latter process suggests that the induced expression of D-type cyclins by mitogenic stimuli might be one of the rate-limiting events for the initiation of lateral roots.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-203X
    Keywords: Abbreviations: 2,4‐D = 2,4‐dichlorophenoxyacetic acid; BA = N6‐benzyladenine; GM = germination medium; GMVIT = germination medium with vitamins; GUS =β‐glucuronidase; Kin = kinetin (N6‐furfurylaminopurine); NAA =α‐naphtaleneacetic acid; NPT II = neomycin phosphotransferase II; PCR = Polymerase Chain reaction; T‐DNA = transfer‐DNA; X‐glucuronide = 5‐bromo‐4‐chloro‐3‐indolyl β‐D‐glucuronide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary. A transfornmation system was developed for Artemisia annua L. plants. Leaf explants from in vitro grown plants developed callus and shoots on medium with 0.05 mg/L naphtaleneacetic acid and 0.5 mg/L N6‐benzyladenine after transformation with the C58Cl RifR (pGV2260) (pTJK136) Agrobacterium tumefaciens strain. A concentration of 20 mg/L kanamycin was added in order to select transformed tissue. Kanamycin resistant shoots were rooted on naphtaleneacetic acid 0.1 mg/L. Polymerase chain reactions and DNA sequencing of the amplification products revealed that 75% of the regenerants contained the foreign genes. 94% of the transgenic plants showed a β‐glucoronidase‐positive response.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A transformation system was developed for Artemisia annua L. plants. Leaf explants from in vitro grown plants developed callus and shoots on medium with 0.05 mg/L naphthaleneacetic acid and 0.5 mg/L N6-benzyladenine after transformation with the C58C1 RifR (pGV2260) (pTJK136) Agrobacterium tumefaciens strain. A concentration of 20 mg/L kanamycin was added in order to select transformed tissue. Kanamycin resistant shoots were rooted on naphthaleneacetic acid 0.1 mg/L. Polymerase chain reactions and DNA sequencing of the amplification products revealed that 75% of the regenerants contained the foreign genes. 94% of the transgenic plants showed a β-glucuronidase-positive response.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1432-2048
    Keywords: Developmental regulation ; Extensin (gene expression) ; Gene expression (extensin) ; Nicotiana (extensin) ; Protein localization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Nicotiana plumbaginifolia Viv. harbors a single extensin gene, although related hydroxyproline-rich sequences are present in the genome. Northern analysis showed that the gene is highly expressed in roots and to a lesser extent in stems. Expression in leaves is low but mRNA levels are increased upon infection with the incompatible bacterium Pseudomonas syringae. Extensin transcript levels in leaves were slightly enhanced after wounding and salicylic acid treatment. In-situ hybridization experiments showed high accumulation of extensin mRNA in cells which, at certain stages of development, require reinforcement of their cell walls. The cortical cells in stem nodes and roots, which are put under severe mechanical stress by adjacent developing tissues, tend to express the gene to high levels. Immunolocalization of the extensin protein in stems and roots demonstrated a close association of the protein with lignin deposition. Mature tissues contained more extensin than younger tissues. The extensin promoter was fused to the β-glucuronidase gene.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1432-2048
    Keywords: Bud dormancy ; Cell cycle ; Populus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The early and differential responses of the individual buds along a shoot have remained largely unknown due to the difficulties of analyzing early indicators that allow the monitoring of the effects of subtle changes in the environment on the growth activity of the individual bud. To overcome this problem, we transformed poplar [Populus tremula (L.) xP. alba (L.)] with two chimeric genes,Pcdc2a-gus andPcycl At-gus, the expression of which is closely linked to cell division inArabidopsis thaliana (L.) Heynh. We analyzed the expression levels of both chimeric genes in individual buds of the same tree, and under different conditions known to promote or retard growth in the buds. The expression levels of both chimeric genes were found to reflect closely the growth activity of the buds. After decapitation of the shoot, the expression ofPcdc2a-gus andPcycl At-gus revealed rapid and selective changes in the cell cycle, even when no morphological changes were observed. Furthermore, on the basis of the expression of the chimeric cell cycle genes, different degrees of growth activity and dormancy could be discriminated in the axillary buds. In addition, the expression ofPcycl At-gus was found to be closely associated with the day length, which is critical for dormancy induction in poplar.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-2048
    Keywords: Key words: Cell cycle –Digitalis– Leafy gall –Nicotiana– Micropropagation – Regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Rhodococcus fascians is a Gram-positive bacterium that infects dicotyledonous and monocotyledonous plants, leading to an alteration in the normal growth process of the host. The disease results from the modulation of the plant hormone balances, and cytokinins are thought to play an important role in the induction of symptoms. Generally, on the aerial parts of the plants, existing meristems were found to be most sensitive to the action of R. fascians, but, depending on the infection procedure, differentiated tissues as well gave rise to shoots. Similarly, in roots not only actively dividing cells, but also cells with a high competence to divide were strongly affected by R. fascians. The observed symptoms, together with the determined hormone levels in infected plant tissue, suggest that auxins and molecules of bacterial origin are also involved in leafy gall formation. The complexity of symptom development is furthermore illustrated by the necessary and continuous presence of the bacteria for symptom persistence. Indeed, elimination of the bacteria from a leafy gall results in the further development of the multiple embryonic buds of which it consists. This interesting characteristic offers novel biotechnological applications: a leafy gall can be used for germplasm storage and for plant propagation. The presented procedure proves to be routinely applicable to a very wide range of plants, encompassing several recalcitrant species.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-203X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Tobacco shooty or rooty teratomas and hairy roots were induced by Agrobacterium tumefaciens (pGV 3845), A. tumefaciens (pGV 3304) and A. rhizogenes (pRi 8196), respectively. The tobacco alkaloids, nicotine, nornicotine and anatabine, were produced in hairy roots and in rooty teratomas but not in shooty teratomas. However, the shooty teratomas have the ability to accumulate the alkaloids and to biotransform nicotine to nornicotine. These were established by co-culture experiments incubating hairy roots and shooty teratomas in a same dish and by biotransformation experiments with shooty teratomas.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1573-5028
    Keywords: cdc2 gene expression ; cell cycle ; Petunia ; protoplast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Analysis of p34cdc2 kinase in higher eukaryotes has demonstrated that p34cdc2 function is conserved in all eukaryotic cells. The p34cdc2 kinase (the product of the cdc2 gene) is required during the G1 cell cycle phase at the initiation of DNA replication and also in G2-M phases for entry into mitosis. In this paper we report the isolation and characterization of a cdc2 Petunia hybrida PCR fragment (cdc2Pet). Using a DNA probe based on this fragment and a p34cdc2-specific antibody, cdc2Pet transcript and p34 protein levels were found to be constant both in 2C nuclei of highly proliferating mesophyll 2C cells derived from protoplasts and in 2C nuclei isolated directly from expanded petunia leaves. Both the cdc2Pet transcript and p34cdc2 protein levels were found to be higher in nuclei at 4C than in those at 2C, even when these 4C nuclei were from non-proliferating tissue. Thus cdc2Pet mRNA and protein levels measured in different tissues should not be interpreted to reflect exclusively the proliferative state of the tissue but also the frequency of G2 cells including those in the differentiated state.
    Type of Medium: Electronic Resource
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