Anticytokinin Effect on Apical Dominance Release in in vitro Cultured Rosa Hybrida L.

Effects of two cytokinin antagonists - 2-chloro-4-cyclobutyl-amino-6-ethylamino-1,3,5-triazine and N-(4-pyridyl)-O-(4-chlorophenyl)carbamate - on bud break and outgrowth in single nodes from two Rosa hybrida cultivars differing in their apical dominance were studied. The compounds were applied at three different concentrations separately or in combination with benzyladenine. Cytokinin antagonists reduced the number of the sprouted buds in both cultivars at different extent. Their effect was strongly dependent on both concentration applied and culture period duration. The replacement of anticytokinins with benzyladenine in the medium resulted in overcoming of the bud break suppression. Both compounds significantly inhibited bud outgrowth as well.     

Alternaria alternata AT Toxin Induces Programmed Cell Death in Tobacco

Detached tobacco leaves were infiltrated with an AT toxin preparation from the foliar pathogen Alternaria alternata tobacco pathotype. The AT toxin preparation caused formation of necrotic lesions within 5 days post-infiltration in a concentration-dependent manner. Cell death was accompanied by increased levels of the stress metabolites hydrogen peroxide, malondialdehyde, free proline and by enhanced total protease activity. Lesion development and the production of stress metabolites were suppressed if the infiltration site was pre-infiltrated with caspase-specific peptide inhibitors (irreversible caspase-1 inhibitor acyl-Tyr-Val-Ala-Asp-chloromethylketone (Ac-YVAD-CMK) and the broad range caspase inhibitor benzyoxycarbonyl-Asp-2,6-dichlorobenzoyloxymethylketone (Z-Asp-CH2-DCB)), the serine protease inhibitor Nα-p-tosyl- l -lysine chloromethylketone and the polyamine spermine. Extensive accumulation of reactive oxygen species (ROS), as determined by staining with 3-3'-diaminobenzidine and 2',7'-dichlorofluorescein diacetate, was found in the AT toxin-challenged lesions. The data show that AT toxin-induced cell death in tobacco is a type of programmed cell death in which caspase-like proteases and ROS signalling play a prominent role.     

Gene structure,transcripts and calciotropic effects of the PTH family of peptides in <Emphasis Type="Italic">Xenopus</Emphasis> and chicken

Background  

Parathyroid hormone (PTH) and PTH-related peptide (PTHrP) belong to a family of endocrine factors that share a highly conserved N-terminal region (amino acids 1-34) and play key roles in calcium homeostasis, bone formation and skeletal development. Recently, PTH-like peptide (PTH-L) was identified in teleost fish raising questions about the evolution of these proteins. Although PTH and PTHrP have been intensively studied in mammals their function in other vertebrates is poorly documented. Amphibians and birds occupy unique phylogenetic positions, the former at the transition of aquatic to terrestrial life and the latter at the transition to homeothermy. Moreover, both organisms have characteristics indicative of a complex system in calcium regulation. This study investigated PTH family evolution in vertebrates with special emphasis on Xenopus and chicken.     

<Emphasis Type="Italic">In vitro</Emphasis> culture of <Emphasis Type="Italic">Hypericum rumeliacum</Emphasis> Boiss. and production of phenolics and flavonoids

The Balkan endemic species, Hypericum rumeliacum, Guttiferae was introduced in vitro for the first time with the aim to study the type of morphogenetic response to plant growth regulators and ability to produce phenolics and flavonoid compounds. The morphoregulatory effect of 2,4-dichlorophenoxyacetic acid (2,4-D), 1-naphtaleneacetic acid (NAA), 6-benzyladenine (BA) and combination of BA with NAA in Murashige–Skoog's basal medium on leaf lamina, internode stem segment, stem node and root cuttings was studied. Histological analysis of the structures regenerated from the primary explants proved the presence of both, embryoids and meristemoids. The node explants cultivated on BA-supplemented medium were the most favourable for regeneration through meristemoids. Therefore a double-stage culture approach, allowing an effective multiplication of large quantities of plant shoots in vitro along with maintenance of the biosynthetic capacity of the culture was developed. It comprised one subculture of three-nodal stem explants derived from the stock shoot cultures on MS medium supplemented with 0.2 mg/l BA followed by subculture of the induced multiple shoots on cytokinin-free MS medium. Determination of the total phenolics and flavonoids showed that the decrease of the levels of these secondary metabolites is transitional, as the exclusionof BA from the medium resulted in an increase of their total content.     

Unusual metastasis of papillary thyroid carcinoma to larynx and hypopharynx a case report

Background  

Although direct infiltration of papillary carcinoma of thyroid to larynx, trachea and esophagus is well recognized, lymphatic and vascular metastases to larynx and hypopharynx have rarely been reported.     

Role of Phenylurea Cytokinin CPPU in Apical Dominance Release in In Vitro Cultured Rosa hybrida L.

Abstract The effect of purine (BA) and phenylurea (CPPU) cytokinins on apical dominance release in in vitro cultured Rosa hybrida L., cv. Madelon and Motrea was evaluated. Cv. Madelon shows stronger natural apical growth and fewer branches than cv. Motrea in vivo and in vitro. We examined the effects under three conditions, without the addition of the auxin IBA, in the presence of IBA, and in material pretreated with a pulse of IBA. Results were scored weekly for 4 weeks. BA and CPPU stimulated axillary bud break, and higher numbers of open buds were recorded in the presence of CPPU. When CPPU cytokinin was added to culture medium, physiologic features such as bud sprouting and shoot fresh and dry weight were enhanced. CPPU was also highly efficient for overcoming IBA inhibition of bud outgrowth. Different cultivar responses were observed. Received 27 April 1999; accepted 23 February 2000     

Effect of Cytokinins and Cytokinin Antagonists on in vitro Cultured Gypsophila paniculata L.

This study deals with the effects of two cytokinins [kinetin (Kin) and N-(2-chloro-4-pyridyl)-N-phenylurea (CPPU)] and cytokinin antagonists [2-chloro-4-cyclobutyl-amino-6-ethylamino-1,3,5-triazine (ACK1) and N-(4-pyridyl)-O-(4-chlorophenyl)carbamate (ACK2)] in concentration of 1 μM on in vitro cultured Gypsophila. The application of Kin and CPPU stimulated bud opening and increased fresh and dry masses. Cytokinin antagonists reduced the number of sprouted buds and bud fresh and dry masses. In plants treated with CPPU the chloroplasts possessed well developed membrane system, which covered almost the entire chloroplasts volume. In ACK2 treated plants, the plastid apparatus in each cell was represented by two types of chloroplast in which the inner membrane system was differently organized. Cell wall adjacent chloroplasts possessed structure similar to the controls. In inner located chloroplasts part of thylakoids were semi-concentrically arranged and partially destructed. This revised version was published online in July 2006 with corrections to the Cover Date.     

Adaptive changes in photosynthetic performance and secondary metabolites during white dead nettle micropropagation

The white dead nettle, Lamium album L., is an herb that has been successfully cultivated under in vitro conditions. The L. album micropropagation system offers a combination of factors (light intensity, temperature, carbon dioxide (CO₂) level, humidity) that are limiting for plant growth and bioactive capacity. To get a better understanding of the mechanism of plant acclimation towards environmental changes, we performed a comparative investigation on primary and secondary metabolism in fully expanded L. album leaves during the consecutive growth in in situ, in vitro, and ex vitro conditions. Although the genetic identity was not affected, structural and physiological deviations were observed, and the level of bioactive compounds was modified. During in vitro cultivation, the L. album leaves became thinner with unaffected overall leaf organization, but with a reduced number of palisade mesophyll layers. Structural deviation of the thylakoid membrane system was detected. In addition, the photosystem 2 (PS2) electron transport was retarded, and the plants were more vulnerable to light damage as indicated by the decreased photoprotection ability estimated by fluorescence parameters. The related CO₂ assimilation and transpiration rates were subsequently reduced, as were the content of essential oils and phenolics. Transfer of the plants ex vitro did not increase the number of palisade numbers, but the chloroplast structure and PS2 functionality were recovered. Strikingly, the rates of CO₂ assimilation and transpiration were increased compared to in situ control plants. While the phenolics content reached normal levels during ex vitro growth, the essential oils remained low. Overall, our study broadens the understanding about the nature of plant responses towards environmental conditions.     

Chloroplast ultrastructure of Hypericum perforatum plants regenerated in vitro after cryopreservation

The ultrastructure of leaf mesophyll cells of in vitro cultured Hypericum perforatum L. plants regenerated after cryopreservation was studied. Electron microscopy analysis revealed that the chloroplasts in plants pretreated with abscisic acid and regenerated after cryopreservation were round, with increased amount of starch, rather small volume of the thylakoid system, and destroyed envelope. Plants pretreated with 0.3 M mannitol and cooled at rates of 0.1 or 0.3 °C min^?1 possessed chloroplasts with high starch content that resulted in a reduction of a membrane system. However, the pretreatment with 0.3 M mannitol and cooling at a rate of 0.2 °C min^?1 was the best as chloroplast ultrastructure resembled the controls regenerated without cryopreservation.