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At least 19 recordsLinked to original sources

Karyological analysis of an interspecific hybrid between the dioecious Silene latifolia and the hermaphroditic Silene viscosa.

The genus Silene is a good model for studying evolution of the sex chromosomes, since it includes species that are hermaphroditic and dioecious, while maintain a basic chromosome number of 2n = 24. For some combinations of Silene species it is possible to construct interspecific hybrids. Here, we present a detailed karyological analysis of a hybrid between the dioecious Silene latifolia as the maternal plant and a related species, hermaphroditic Silene viscosa, used as a pollen partner. Using genomic probes (the genomic in situ hybridization (GISH) technique), we were able to clearly discriminate parental genomes and to show that they are largely separated in distinct nuclear domains. Molecular GISH and fluorescence in situ hybridization (FISH) markers document that the hybrid genome of somatic cells was strictly additive and stable, and that it had 12 chromosomes originating from each parent, including the only X chromosome of S. latifolia. Meiotic analysis revealed that, although related, respective parental chromosomes did not pair or paired only partially, which resulted in frequent chromosome abnormalities such as bridges and irregular non-disjunctions. GISH and FISH markers clearly document that the larger genome of S. latifolia and its largest chromosome component, the X chromosome, were mostly employed in chromosome lagging and misdivision.

Chimera↗

DNA diversity in sex-linked and autosomal genes of the plant species Silene latifolia and Silene dioica.

The relatively recent origin of sex chromosomes in the plant genus Silene provides an opportunity to study the early stages of sex chromosome evolution and, potentially, to test between the different population genetic processes likely to operate in nonrecombining chromosomes such as Y chromosomes. We previously reported much lower nucleotide polymorphism in a Y-linked gene (SlY1) of the plant Silene latifolia than in the homologous X-linked gene (SlX1). Here, we report a more extensive study of nucleotide diversity in these sex-linked genes, including a larger S. latifolia sample and a sample from the closely related species Silene dioica, and we also study the diversity of an autosomal gene, CCLS37.1. We demonstrate that nucleotide diversity in the Y-linked genes of both S. latifolia and S. dioica is very low compared with that of the X-linked gene. However, the autosomal gene also has low DNA polymorphism, which may be due to a selective sweep. We use a single individual of the related hermaphrodite species Silene conica, as an outgroup to show that the low SlY1 diversity is not due to a lower mutation rate than that for the X-linked gene. We also investigate several other possibilities for the low SlY1 diversity, including differential gene flow between the two species for Y-linked, X-linked, and autosomal genes. The frequency spectrum of nucleotide polymorphism on the Y chromosome deviates significantly from that expected under a selective-sweep model. However, we detect population subdivision in both S. latifolia and S. dioica, so it is not simple to test for selective sweeps. We also discuss the possibility that Y-linked diversity is reduced due to highly variable male reproductive success, and we conclude that this explanation is unlikely.

DNA, Plant↗

Physical mapping, expression patterns and interphase organisation of rDNA loci in Portuguese endemic Silene cintrana and Silene rothmaleri.

Double target in situ hybridization to root tip metaphase and interphase cells of Silene cintrana and Silene rothmaleri was used to allocate the position of 18S-5.8S-25S and 5S rRNA genes. In both species, the 18S-5.8S-25S rDNA probe labelled four sites located on the short arms of two submetacentric chromosomes. Only one locus for 5S rDNA was mapped adjacent to 18S-5.8S-25S genes in a subterminal position on the centromere side: in S. rothmaleri the 5S rDNA locus was adjacent to the small 18S-5.8S-25S locus while in S. cintrana it was near the large one. The NOR activity analysed by Ag-staining in metaphase cells revealed proportionality between in situ labelling dimensions and Ag-NORs. In both species all rDNA loci were potentially active, although in S. rothmaleri a tendency for the expression of only one locus was observed. Interphase organisation analysis of rDNA showed some differences between both species that were correlated with NOR activity.

Centromere↗

Sex ratio in hybrids between Silene alba and Silene dioica: evidence for Y-linked restorers.

Sex ratio in Silene alba is generally female biased, and the bias is influenced by Y-linked alleles that are polymorphic in natural populations. One interpretation of these alleles is that they enhance the production of males in female-biased populations, i.e. they are restorers. Two Silene species, S. alba and S. dioica, and their reciprocal hybrids were used to investigate the inheritance of sex ratio and the relationship between sex ratio and male fertility. Sex ratio was paternally inherited (i.e. Y-linked), but was also strongly influenced by the maternal parent through an interaction with the Y chromosome. These results corroborate previous work on the inheritance of sex ratio within S. alba, and suggest that sex ratio in S. alba and S. dioica has a similar genetic basis. Examination of the maternal by Y chromosome interaction revealed that the Y chromosome of each species produced a more severe female bias in crosses with females of the opposite species. This is consistent with the hypothesis that the alleles expressed in the maternal parent cause the female bias, while the Y-linked alleles tend to restore sex ratio toward equality.

Crosses, Genetic↗

Use of Internal Transcribed Spacer Primers and Fungicide Treatments to Study the Anther-Smut Disease, Microbotryum violaceum (=Ustilago violacea), of White Campion Silene alba (=Silene latifolia).

We report the construction and use of polymerase chain reaction (PCR) primers for detection of Microbotryum violaceum in Silene alba. Such primers show that the pathogen is present in the aboveground bud meristems, flower pedicels, and flower-stem internodes but not in the flowering-stem leaves and roots of flowering plants. Use of primers also showed that the pathogen was absent from plants that had been inoculated with the fungus but remained healthy. The fungicides Folicur and Bayleton cured plants of the disease, and the absence of the fungus from such cured plants was confirmed using the PCR primers.

Journal Article↗

Zwitterionic silenes: interesting goals for synthesis?

Properties of silenes, as a function of increased reversal of the Si=C bond polarity, have been examined through quantum-chemical calculations. The aim of this study was to identify silenes that can be of general interest for organic synthesis. The calculations were carried out primarily with the B3LYP hybrid density functional method, but also with the CASSCF, MP2, MP4(SDQ), and CCSD(T) methods. The study was performed on Z(2)Si=CXY compounds which were divided into three sets that differ with regard to their Si substituents (Z), and with their C substituents (X and Y) varying from weakly to strongly pi-electron-donating groups. The charge at the Si atom (q(Si)) was used as a measure of the extent of reversed silicon-carbon bond polarity. For each of the three sets, the variation in silicon-carbon bond lengths (r(Si=C)) and extent of Si pyramidalization (SigmaSi) in relation to q(Si) follow three separate curves. Silenes with strongly pi-electron-donating X and Y groups are completely described by zwitterionic (reverse-polarized) resonance structures. Such zwitterionic silenes are singly (Si=C) rather than doubly bonded (Si=C), and have a distinctly pyramidal Si atom due to negative charge localization. These silenes also have much lower heats of dimerization than the parent silene. Finally, inversion barriers of zwitterionic silenes are increased by electron-withdrawing substituents, and this enables computational design of silenes with their Si atoms as chiral centers. It is hoped that such chiral zwitterionic silenes can find use in organic synthesis.

Journal Article↗

Identification and quantitative analysis of the phytoecdysteroids in Silene species (Caryophyllaceae) by high-performance liquid chromatography. Novel ecdysteroids from S. pseudotites.

Many species in the genus Silene (Caryophyllaceae) have previously been shown to contain ecdysteroids and this genus is recognised as a good source of novel ecdysteroid analogues. We have used ecdysteroid-specific radioimmunoassays and the microplate-based Drosophila melanogaster B(II) cell bioassay for ecdysteroid agonist and antagonist activities to identify further phytoecdysteroid-containing species in this genus. The main ecdysteroid components from 10 Silene species (S. antirrhina, S. chlorifolia, S. cretica, S. disticha, S. echinata, S. italica, S. portensis, S. pseudotites, S. radicosa, S. regia) were isolated and identified, mainly by normal-phase and reversed-phase high-performance liquid chromatography. The amount of each ecdysteroid was determined by comparing chromatogram peak areas with those for reference 20-hydroxyecdysone (20E) on reversed-phase HPLC. 20E is the most abundant ecdysteroid in each of the Silene extracts. Polypodine B, 2-deoxy-20-hydroxyecdysone and ecdysone are also common ecdysteroids in these Silene species, but the proportions of these ecdysteroids vary between the Silene species. HPLC proved to be a quick and effective way to screen Silene species, determine ecdysteroid profiles and, hence, identify extracts containing novel analogues. An extract of the aerial parts of S. pseudotites was found to contain several new ecdysteroids. These have been isolated and identified spectroscopically (by NMR and mass spectrometry) as 2-deoxyecdysone 22beta-D-glucoside, 2-deoxy-20,26-dihydroxyecdysone and 2-deoxypolypodine B 3beta-D-glucoside. Additionally, (5alpha-H)-2-deoxyintegristerone A (5alpha-2H 91%, 5alpha-1H 9%) was isolated as an artefact. This study contributes to the understanding of ecdysteroid distribution in Silene species and provides further information on the chemotaxonomic significance of ecdysteroids in Silene species.

Caryophyllaceae↗

Synthesis and structural characterization of novel silenes stabilized by intramolecular coordination of a dialkylamino group.

Two intramolecularly donor-stabilized silenes, 1-(8-dimethylamino-1-naphthyl)-1,2,2-tris(trimethylsilyl)silene (6a) and 1-(2-dimethylaminomethylphenyl)-1,2,2-tris(trimethylsilyl)silene (6b), were synthesized according to a novel one-step process by the reaction of (dichloromethyl)tris(trimethylsilyl)silane (1) with a twofold molar excess of 8-dimethylamino-1-naphthyllithium or 2-(dimethylaminomethyl)phenyllithium, respectively. Compounds 6a and 6b are thermally stable compounds. X-ray structural analyses of both silenes revealed strong donor-acceptor interactions between the dialkylamino groups and the electrophilic silene silicon atoms (Si-N distances: 6a: 1.751(3) A; 6b: 1.749(3) A) that lead to pyramidalization at the silicon centers. In contrast, the configuration at the silene carbon atoms was found to be planar. The Si=C distances (6a: 1.751(3) A; 6b: 1.749(3) A) fit with literature data of comparable compounds. Addition of water or methanol to the Si=C bonds of 6a,b afforded the silanols 7a,b and the methoxysilanes 8a,b, respectively. The compound 1-(8-dimethylaminomethyl-1-naphthyl)-1,2,2-tris(trimethylsilyl)silene (6c), generated following the same procedure by the reaction of 1 with 8-(dimethylaminomethyl)-1-naphthyllithium (molar ratio 1:2) proved to be unstable at room temperature and underwent rapid insertion of the Si=C group into a methylene C-H bond of the dimethylaminomethylnaphthyl ligand to afford the 1-silaacenaphthene 9.

Journal Article↗

Addition of cyclopropyl alkynes to a Brook silene: definitive evidence for a biradical intermediate.

The addition of three newly developed mechanistic probes, (trans-2-phenylcyclopropyl)ethyne, (trans,trans-2-methoxy-3-phenylcyclopropyl)ethyne, and (trans,trans-2-methoxy-1-methyl-3-phenylcyclopropyl)ethyne, 1a-c, to a Brook silene, 2-tert-butyl-2-trimethylsiloxy-1,1-bis(trimethylsilyl)-1-silene, 10, was examined. When alkyne 1a was added to silene 10 products derived from a formal ene reaction were obtained. When alkynes 1b-c were added to silene 10, in addition to the typical silacyclobutenes, a variety of silacycloheptenes were obtained in which the cyclopropyl ring had clearly opened. Formal ene-addition products were also produced from the addition of 1b to 10. Based on the relative positions of the phenyl and methoxy substituents within the seven-membered ring of the silacycloheptenes and the known behavior of the alkyne probes under both radical and ionic conditions, it was concluded that a biradical intermediate was formed during the addition of alkynes 1b-c to silene 10. In the addition of alkynes 1a-b to silene 10, the ene products are most likely formed by a competitive pericyclic reaction. We also present a straightforward method for the unambiguous determination of the regiochemistry of silacyclobutenes derived from the cycloaddition of terminal alkynes to silenes.

Journal Article↗

Gibberellins and Stem Growth as Related to Photoperiod in Silene armeria L.

Stem growth and flowering in the long-day plant Silene armeria L. are induced by exposure to a minimum of 3 to 6 long days (LD). Stem growth continues in subsequent short days (SD), albeit at a reduced rate. The growth retardant tetcyclacis inhibited stem elongation induced by LD, but had no effect on flowering. This indicates that photoperiodic control of stem growth in Silene is mediated by gibberellins (GA). The objective of this study was to analyze the effects of photoperiod on the levels and distribution of endogenous GAs in Silene and to determine the nature of the photoperiodic after-effect on stem growth in this plant. The GAs identified in extracts from Silene by full-scan combined gas chromatography-mass spectrometry (GC-MS), GA(12), GA(53), GA(44), GA(17), GA(19), GA(20), GA(1), GA(29), and GA(8), are members of the early 13-hydroxylation pathway. All of these GAs were present in plants under SD as well as under LD conditions. The GA(53) level was highest in plants in SD, and decreased in plants transferred to LD conditions. By contrast, GA(19), GA(20), and GA(1) initially increased in plants transferred to LD, and then declined. Likewise, when Silene plants were returned from LD to SD, there was an increase in GA(53), and a decrease in GA(19), GA(20), and GA(1) which ultimately reached levels similar to those found in plants kept in SD. Thus, measurements of GA levels in whole shoots of Silene as well as in individual parts of the plant suggest that the photoperiod modulates GA metabolism mainly through the rate of conversion of GA(53). As a result of LD induction, GA(1) accumulates at its highest level in shoot tips which, in turn, results in stem elongation. In addition, LD also appear to increase the sensitivity of the tissue to GA, and this effect is presumably responsible for the photoperiodic after-effect on stem elongation in Silene.

Journal Article↗

A combined experimental and theoretical study of the kinetics and mechanism of the addition of alcohols to electronically stabilized silenes: a new mechanism for the addition of alcohols to the Si=C bond.

The stabilized silene 1,1-bis(trimethylsilyl)-2-adamantylidenesilane (4) has been generated by photolysis of a novel trisilacyclobutane derivative in various solvents and studied directly by kinetic UV spectrophotometry. Silene 4 decays with second-order kinetics in degassed hexane solution at 23 degrees C (k/epsilon = 8.6 x 10(-6) cm s(-1)) due to head-to-head dimerization. It reacts rapidly with oxygen [k(25 degrees C) approximately 3 x 10(5) M(-1) s(-1)] but approximately 10 orders of magnitude more slowly with methanol (MeOH) than other silenes that have been studied previously. The data are consistent with a mechanism involving reaction with the hydrogen-bonded dimer of the alcohol, (MeOH)(2) (k = 40 +/- 3 M(-1) s(-1); k(H)/k(D) = 1.7 +/- 0.2). The stable analogue of silene 4, 1-tert-butyldimethylsilyl-1-trimethylsilyl-2-adamantylidenesilane (5), reacts approximately 50 times more slowly, but via the same mechanism. The mechanism for addition of water and methanol (ROH; R = H, Me) to 4, 5, and the model compound 1,1-bis(silyl)-2,2-dimethylsilene (3a) has been studied computationally at the B3LYP/6-31G(d) and MP2/6-31G(d) levels of theory. Hydrogen-bonded complexes with monomeric and dimeric methanol, in which the Si=C bond plays the role of nucleophile, have been located computationally for all three silenes. Reaction pathways have been characterized for reaction of the three silenes with monomeric and dimeric ROH and reveal significantly lower barriers for reaction with the dimeric form of the alcohol in each case. The calculations indicate that 5 should be approximately 40-fold less reactive toward dimeric MeOH than 4, in excellent agreement with the approximately 50-fold difference in the experimental rate constants for reaction in hexane solution.

Journal Article↗

Kinetic and cross-linking studies on the interactions of negative patch mutant plastocyanin from Silene pratensis with photosystem I complexes from cyanobacteria, green algae, and plants.

The site-directed mutants of negative patches on silene plastocyanin (PC) were used to investigate the change of interactions between photosystem I (PSI) and PC during the course of evolution from cyanobacteria to plants. The net charges of two highly conserved negative patches (#42-45 and #59-61) on silene PC were systematically modified from -4 to +1. PSI complexes from cucumber and Chlamydomonas reinhardtii were efficient electron acceptors for silene PC. The increase of net charge on the negative patch (#42-45) of silene PC decreased the reduction rates of PSI from cucumber and Chlamydomonas, while the modification of the other negative patch (#59-61) had no effect. Though the addition of MgCl2 decreased the reduction rate of cucumber PSI, the decrease was severely diminished in the case of Chlamydomonas PSI, and the reduction rate increased with increasing concentration of MgCl2 when the net charge of the negative patch (#42-45) was modified to +1. The PSI complexes from Anabaena variabilis and Synechosystis sp. PCC 6803 were inefficient electron acceptors for silene PC and their rates were almost independent of the net charge of the negative patches, as well as the ionic strength of the reaction mixtures. Silene PC specifically cross-linked to the PsaF subunit of PSI complexes from cucumber, Chlamydomonas, Anabaena, and Synechosystis sp. PCC 6803. Modification of the negative patch (#42-45) inhibited the formation of cross-linked adducts in all the cases examined, whereas modification of the other negative patch (#59-61) had essentially no effect. Based on these results, the changes of electrostatic interactions between PC and PSI during the course of evolution from cyanobacteria to plants are discussed.

Amino Acid Sequence↗

C-banded karyotypes of two Silene species with heteromorphic sex chromosomes.

Mitotic metaphase chromosomes of Silene latifolia (white campion) and Silene dioica (red campion) were studied and no substantial differences between the conventional karyotypes of these two species were detected. The classification of chromosomes into three distinct groups proposed for S. latifolia by Ciupercescu and colleagues was considered and discussed. Additionally, a new small satellite on the shorter arm of homobrachial chromosome 5 was found. Giemsa C-banded chromosomes of the two analysed species show many fixed and polymorphic heterochromatic bands, mainly distally and centromerically located. Our C-banding studies provided an opportunity to better characterize the sex chromosomes and some autosome types, and to detect differences between the two Silene karyotypes. It was shown that S. latifolia possesses a larger amount of polymorphic heterochromatin, especially of the centromeric type. The two Silene sex chromosomes are easily distinguishable not only by length or DNA amount differences but also by their Giemsa C-banding patterns. All Y chromosomes invariably show only one distally located band, and no other fixed or polymorphic bands on this chromosome were observed in either species. The X chromosomes possess two terminally located fixed bands, and some S. latifolia X chromosomes also have an extra-centric segment of variable length. The heterochromatin amount and distribution revealed by our Giemsa C-banding studies provide a clue to the problem of sex chromosome and karyotype evolution in these two closely related dioecious Silene species.

Chromosome Banding↗

Gibberellins in Relation to Flowering and Stem Elongation in the Long Day Plant Silene armeria.

Two long days induced some flowering and 4 or more long days caused 100% flowering in Silene armeria. On long days microscopically detectable flower primordia were first seen after 6 days, which is at least 1 day before the start of stem elongation. Both gibberellin A(3) and A(7) caused flowering on short days, but the results were variable and flowering was never 100%. Three different gibberellins were detected in Silene extracts. The pattern of gibberellins extracted from plants on short and long days was qualitatively the same, but on long days gibberellin content was up to 100% higher than on short days. Only small amounts of diffusible gibberellins were obtained from Silene shoot tips (including very young leaves) on short days. However, on long days the diffusible gibberellins increased by as much as 10-fold after 4 to 6 long days but then declined somewhat after 10 long days. The gibberellins extracted from the shoot tips at the completion of the diffusion period also increased under long days, although the increase was not as large as for the diffusible gibberellins. An A(5)-like gibberellin present in extracts was not detected in diffusates.Treatment with AMO 1618 (2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine-carboxylate methyl chloride) completely inhibited stem elongation on long days but had no effect on flowering. In addition, treatment with AMO 1618 caused at least an 80% decrease in the level of extractable gibberellin, while the diffusible gibberellin was reduced below the limits of detection in the d5 corn bioassay. When endogenous gibberellin levels were suppressed by pretreatment with AMO 1618 on short days, gibberellin A(3) caused more stem elongation in plants moved to long days than in plants left on short days. Thus the sensitivity of Silene plants to gibberellin with respect to stem growth is affected by photoperiod. It is concluded that in Silene endogenous gibberellins are a controlling factor for stem elongation but apparently are not required for flower formation.

Journal Article↗

Copper uptake by Elsholtzia splendens and Silene vulgaris and assessment of copper phytoavailability in contaminated soils.

Tolerance and metal uptake are two essential characteristics required for phytoextraction of metals from contaminated soils. We compared tolerance and Cu uptake of Elsholtzia splendens (reported previously to be a Cu hyperaccumulator) with Silene vulgaris (the Imsbach population, a well-known Cu-tolerant excluder species), using 30 soils varying widely in total Cu concentration (19-8645 mg kg(-1)). We further investigated the effectiveness of different soil testing methods for predicting plant metal uptake. The results showed that both Elsholtzia splendens and Silene vulgaris were tolerant to Cu, especially Silene vulgaris. However, Elsholtzia splendens did not hyperaccumulate Cu, but behaved as a typical Cu excluder like Silene vulgaris. The concentrations of Cu in both plants correlated more closely with 1 M NH4NO3 extractable Cu, soil solution Cu, or effective Cu concentration determined using DGT, than with soil total Cu, EDTA extractable Cu or free Cu2+ activity. The relationships between soil solution properties and root Cu concentrations were further investigated using multiple regression. The results showed that increasing soil solution pH increased root Cu concentration when free Cu2+ activity was held constant, suggesting a higher phytoavailability of free Cu2+ at a higher pH. Soil solution DOC appeared to play two contrasting roles on the phytoavailability of Cu: (1) reducing Cu availability by complexing Cu; and (2) increasing Cu availability at the same level of free Cu2+ activity by providing a strong buffer for free Cu2+. The results are consistent with the intensity/capacity concept for phytoavailability of metals in soils.

Copper↗

LTR retrotransposons in the dioecious plant Silene latifolia.

Conserved domains of two types of LTR retrotransposons, Tyl-copia- and Ty3-gypsy-like retrotransposons, were isolated from the dioecious plant Silene latifolia, whose sex is determined by X and Y chromosomes. Southern hybridization analyses using these retrotransposons as probes resulted in identical patterns from male and female genomes. Fluorescence in situ hybridization indicated that these retrotransposons do not accumulate specifically in the sex chromosomes. These results suggest that recombination between the sex chromosomes of S. latifolia has not been severely reduced. Conserved reverse transcriptase regions of Ty1-copia-like retrotransposons were isolated from 13 different Silene species and classified into two major families. Their categorization suggests that parallel divergence of the Ty1-copia-like retrotransposons occurred during the differentiation of Silene species. Most functional retrotransposons from three dioecious species, S. latifolia, S. dioica, and S. diclinis, fell into two clusters. The evolutionary dynamics of retrotransposons implies that, in the genus Silene, dioecious species evolved recently from gynodioecious species.

Amino Acid Sequence↗

Heterogeneity of rDNA distribution and genome size in Silene spp.

Genus Silene L. (Caryophyllaceae) contains about 700 species divided into 44 sections. According to recent taxonomic classification this genus also includes taxa previously classified in genera Lychnis and Melandrium. In this work, four Silene species belonging to different sections were studied: S. latifolia (syn. Melandrium album, Section Elisanthe), S. vulgaris (Inflatae), S. pendula (Erectorefractae), and S. chalcedonica (syn. Lychnis chalcedonica, Lychnidiformes). Flow cytometric analysis revealed a genome size of 2.25 and 2.35 pg/2C for S. vulgaris and S. pendula and of 5.73 and 6.59 pg/2C for S. latifolia and S. chalcedonica. All four species have the same chromosome number including the pair of sex chromosomes of the dioecious S. latifolia (2n = 2x = 24). Double target fluorescence in-situ hybridization revealed the chromosomal locations of 25S rDNA and 5S rDNA. A marked variation in number and localization of rDNA loci but no correlation between the numbers of rDNA clusters and genome size was found. FISH and genome size data indicate that nuclear genomes of Silene species are highly diversified as a result of numerous DNA amplifications and translocations.

Cell Nucleolus↗