Hybridization and karyotype variability of three endemic Fritillaria L. (Liliaceae) in Argolis Peninsula (Greece)

Abstract

The Argolis Peninsula covers the north-eastern part of Peloponnisos and is surrounded by the Gulf of Argosaronic. The area hosts three species of the genus Fritillaria: F. graeca, F. rhodocanakis and F. spetsiotica. Fritillaria graeca is a Greek endemic taxon and its distribution includes Peloponnisos, C & E Sterea Ellas, C Evia and in proximity to Sterea Ellas, Salamis and Kea islands, while the stenoendemic F. rhodocanakis and F. spetsiotica are mainly found on Idra and Spetses islands respectively. The last two taxa are included in the Red Data Book of Rare and Threatened Plants of Greece, while F. rhodocanakis is also included in the IUCN Red List. Hybridization among them is a common phenomenon in the areas where they coexist, leading to an array of morphologically and karyologically intermediate forms. The current study presents the taxa’s karyomorphometric analysis for the first time and reveals hybrids’ cytological variety, including differences in marker chromosomes, polyploidy and the number of B-chromosomes.     

The decisive role of the water structure in changes of conformation of nucleic acids.

This review summarizes data on the structure and properties of water under normal conditions, at high salt concentration and under high pressure. We correlate the observed conformational transitions in nucleic acids with changes in water structure and activity, and suggest a mechanism of conformational transitions of nucleic acid involving these changes. We conclude that the Z-DNA form is induced only at low water activity caused by high salt concentrations and/or high pressure.     

Structural analysis of 5S rRNA, 5S rRNA-protein complexes and ribosomes employing RNase H and d(GTTCGG)

The hybridization of d(GTTCGG) to eubacterial 5S rRNAs, 5S rRNA-protein complexes, 70S ribosomes and 50S and 30S ribosomal subunits was investigated. This oligonucleotide, which may be considered to be an analogue of the T psi CG loop of tRNAs, was chosen in order to investigate a possible interaction between tRNAs with ribosomal components during protein synthesis. The hybridization was analysed by RNase H hydrolysis studies and, in the case of the ribosomes and ribosomal subunits, in addition with the radioactively labelled oligodeoxyribonucleotide in binding studies. The results obtained lead to the conclusion that nucleotides in loop c, i.e. positions 42-47, are available for oligonucleotide interaction in free Escherichia coli and Bacillus stearothermophilus 5S rRNAs and not available in the corresponding 5S rRNA-protein complexes. The 70S ribosomes and ribosomal subunits did not interact with the oligonucleotide. Under the assumption that d(GTTCGG) is an analogue of the T psi CG loop of tRNAs and in view of the results obtained, we conclude that in the unprogrammed ribosomes the T psi CG loop of tRNAs does not interact via standard Watson-Crick base pairs with the ribosomal 5S, 16S or 23S RNAs.     

Increased number of cardiac adrenergic receptors following local heart irradiation

The effect of local X irradiation on cardiac alpha and beta receptors was studied in Wistar rats. Animals were given local heart irradiation with single doses of 15 or 20 Gy and were examined after a range of latency times of 7 to 400 days. Using the radioactive ligands [3H]CGP-12177 and [3H]prazosin, the maximal binding capacity was determined from saturation experiments. At 7 days after 20 Gy the maximal binding capacity of both alpha and beta receptors was reduced to below the level of untreated control animals. Subsequently it rose continually to a maximum of 160% of the control level for beta receptors and 130% for alpha receptors at 400 days postirradiation. The antagonist affinity as judged from the dissociation constant for [3H]CGP 12177 and [3H]prazosin did not change significantly. A similar effect was observed after 15 Gy. An increase in adrenergic receptors may represent an important pathogenetic link between early morphological and late functional changes in the pathogenesis of radiation-induced heart disease.     

Natural15N abundance as a method of estimating the contribution of biologically fixed nitrogen to N2-fixing systems: Potential for non-legumes

The¹⁵N abundance of plants usually closely reflects the¹⁵N abundance of their major immediate N source(s); plant-available soil N in the case of non-N₂-fixing plants and atmospheric N₂ in the case of N₂ fixing plants. The¹⁵N abundance values of these sources are usually sufficiently different from each other that a significant and systematic difference in the¹⁵N abundance between the two kinds of plants can be detected. This difference provides the basis for the natural¹⁵N abundance method of estimating the relative contribution of atmospheric N₂ to N₂-fixing plants growing in natural and agricultural settings. The natural¹⁵N abundance method has certain advantages over more conventional methods, particularly in natural ecosystems, since disturbance of the system is not required and the measurements may be made on samples dried in the field. This method has been tested mainly with legumes in agricultural settings. The tests have demonstrated the validity of this method of arriving at semi-quantitative estimates of biological N₂-fixation in these settings. More limited tests and applications have been made for legumes in natural ecosystems. An understanding of the limits and utility of this method in these systems is beginning to emerge. Examples of systematic measurements of differences in¹⁵N abundance between non-legume N₂-fixing systems and neighbouring non-fixing systems are more unusual. In principle, application of the method to estimate N₂-fixation by nodulated non-legumes, using the natural¹⁵N abundance method, is as feasible as estimating N₂-fixation by legumes. Most of the studies involving N₂-fixing non-legumes are with this type of system (e.g., Ceanothus, Chamabatia, Eleagnus, Alnus, Myrica, and so forth). Resuls of these studies are described. Applicability for associative N₂-fixation is an empirical question, the answer to which probably depends upon the degree to which fixed N goes predominantly to the plant rather than to the soil N pool. The natural¹⁵N abundance method is probably not well suited to assessing the contribution of N₂-fixation by free-living microorganisms in their natural habitat, particularly soil microorganisms.This work was supported in part by subcontracts under grants from the US National Science Foundation (DEB79-21971 and BSR821618)     

Improved procedure for the isolation of a double-strand-specific ribonuclease and its application to structural analysis of various 5S rRNAs and tRNAs

An improved method for the isolation of a double-strand-specific RNase from snake venom is presented. This RNase, called CSV, was used to cleave yeast tRNAPhe and tRNA2Glu and tRNAfMet from Escherichia coli. In addition these RNAs and E. coli tRNAPhe were examined with the single-strand-specific nuclease S1. The results are discussed in terms of the specificity of CSV RNase and the structure of tRNAs. S1 nuclease digestions at increasing temperatures allowed the melting of tertiary and secondary structure to be monitored. 5S rRNA from E. coli, Thermoplasma acidophilum and the chloroplasts of Spinacia oleracea were digested with CSV and S1. The information these results give on the secondary-structural differences between different classes of 5S rRNA are discussed. Supporting evidence is found for tertiary interactions between hairpin loop c and internal loop d of eubacterial 5S rRNA.