Nuclear architecture in plants

Nuclei are dynamic structures that move through the mitotic cell cycle, are involved in differentiation, and divide and fuse during reproduction. The DNA contents of nuclei from different plants vary by 2500-fold. The design and structure of nuclei is, therefore, both flexible and versatile. Features relating to genome, chromosome, and maybe even gene localization during interphase are now emerging. At the chromosomal level, studies of scaffold associations and DNA sequence organization are indicating structures that impose nuclear architecture.     

Time relationships of sporopollenin synthesis associated with tapetum and microspores in Lilium

Summary The development of the sporopollenin orbicules (Ubisch bodies) on the tapetal cells of Lilium begins while the spores are still enclosed in the meiotic tetrads. Spherosome-like structures, the pro-orbicular bodies, accumulate in the vicinity of the plasmalemma early in the tetrad period, and are extruded into the space within the degenerating inner walls of the tapetal cells. There they acquire a coating of sporopollenin, the accretion continuing until after the release of the spores from the tetrads. Some orbicules remain attached to the plasmalemma by stalks. Synthesis of a material of the general class of sporopollenin begins in the primexine of the young spore in the mid-tetrad period, again outside of the cell membrane, but within the callose tetrad wall.A general scheme for sporopollenin formation in the anther is given. According to this, (a) precursors are synthesised both in the young spores and in the tapetum, and released into the extracellular space; and (b) polymerisation occurs on initiating sites outside of the cell membranes, these sites being the surface of the proorbicular bodies and of the special lamellae concerned in exine growth.Synthesis of sporopollenin in the anther is virtually complete before the main synthesis of the pigmented pollen coat substances (Pollenkitt) begins in the tapetum. It is therefore improbable that the carotenoids produced in the final phase of metabolic activity in the tapetum can be sporopollenin precursors.

---

Zusammenfassung Die Entwicklung der Sporopollenin-Orbicula (Ubisch-Körper) in den Tapetenzellen von Lilium beginnt wenn die Sporen noch in den meiotischen Tetraden zusammen geschlossen sind. Sphärosomenähnliche Gebilde, die Pro-Orbicularkörper, werden im frühen Tetradenstadium in der Nähe des Plasmalemmas angehäuft und dann in den Raum innerhalb der degenerierenden Innenwände der Tapetenzellen ausgestoßen. Dort werden sie mit einer Hülle aus Sporopollenin versehen; dieser Vorgang dauert noch an, wenn die Sporen aus dem Tetradenverband freigesetzt worden sind. Einige der Orbicular bleiben mit dem Plasmalemma mittels Stielchen verbunden. Im mittleren Tetradenstadium setzt in den Primexinen der jungen Sporen die Synthese eines Materials ein, welches der allgemeinen Klasse der Sporopollenine angehört; auch dieser Vorgang verläuft außerhalb der Zellmembran, aber innerhalb der aus Callose bestehenden Tetradenwand.Ein allgemeines Schema für Sporenpollenbildung in der Anthere wird vorgeschlagen. Danach werden a) Vorstufen sowohl in der jungen Spore als auch im Tapetum synthetisiert und in den extracellulären Raum ausgeschieden, und b) findet Polymerisation an spezifischen Stellen außerhalb der Zellmembran, und zwar den Oberflächen der Pro-Orbicularkörper und der für das Wachstum der Exine maßgeblichen, speziellen Lamellen, statt.Die Synthese des Sporopollenins in der Anthere ist praktisch beendet bevor die Synthese der pigmentierten Substanzen der Pollenhaut (Pollenkitt) im Tapetum einsetzt. Es ist daher unwahrescheinlich, daß die Carotinoide, die in den Endstadien der Stoffwechseltätigkeit der Tapetenzellen gebildet werden, Vorstufen des Sporopollenins sein können.

     

A new 2D-based method for myocardial velocity strain and strain rate quantification in a normal adult and paediatric population: assessment of reference values

Background

Cardiac time intervals have been described as a measure of cardiac performance, where prolongation, shortening and delay of the different time intervals have been evaluated as markers of cardiac dysfunction. A relatively recently developed method with improved ability to measure cardiac events is Tissue Doppler Imaging (TDI), allowing accurate measurement of myocardial movements.

Methods

We propose the state diagram of the heart as a new visualization tool for cardiac time intervals, presenting comparative, normalized data of systolic and diastolic performance, providing a more complete overview of cardiac function. This study aimed to test the feasibility of the state diagram method by presenting examples demonstrating its potential use in the clinical setting and by performing a clinical study, which included a comparison of the state diagram method with established echocardiography methods (E/E' ratio, LVEF and WMSI). The population in the clinical study consisted of seven patients with non ST-elevation myocardial infarction (NSTEMI) and seven control subjects, individually matched according to age and gender. The state diagram of the heart was generated from TDI curves from seven positions in the myocardium, visualizing the inter- and intraventricular function of the heart by displaying the cardiac phases.

Results

The clinical examples demonstrated that the state diagram allows for an intuitive visualization of pathological patterns as ischemia and dyssynchrony. Further, significant differences in percentage duration between the control group and the NSTEMI group were found in eight of the totally twenty phases (10 phases for each ventricle), e.g. in the transition phases (Pre-Ejection and Post-Ejection). These phases were significantly longer (> 2.18%) for the NSTEMI group than for the control group (p < 0.05). No significant differences between the groups were found for the established echocardiography methods.

Conclusion

The test results clearly indicate that the state diagram has potential to be an efficient tool for visualization of cardiac dysfunction and for detection of NSTEMI.     

Systems analysis of iron metabolism: the network of iron pools and fluxes

Background  

Every cell of the mammalian organism needs iron as trace element in numerous oxido-reductive processes as well as for transport and storage of oxygen. The very versatility of ionic iron makes it a toxic entity which can catalyze the production of radicals that damage vital membranous and macromolecular assemblies in the cell. The mammalian organism maintains therefore a complex regulatory network of iron uptake, excretion and intra-body distribution. Intracellular regulation in different cell types is intertwined with a global hormonal signalling structure. Iron deficiency as well as excess of iron are frequent and serious human disorders. They can affect every cell, but also the organism as a whole.     

The repetitive component of the A genome of peanut (Arachis hypogaea) and its role in remodelling intergenic sequence space since its evolutionary divergence from the B genome

Background and Aims

Peanut (Arachis hypogaea) is an allotetraploid (AABB-type genome) of recent origin, with a genome of about 2·8 Gb and a high repetitive content. This study reports an analysis of the repetitive component of the peanut A genome using bacterial artificial chromosome (BAC) clones from A. duranensis, the most probable A genome donor, and the probable consequences of the activity of these elements since the divergence of the peanut A and B genomes.

Methods

The repetitive content of the A genome was analysed by using A. duranensis BAC clones as probes for fluorescence in situ hybridization (BAC-FISH), and by sequencing and characterization of 12 genomic regions. For the analysis of the evolutionary dynamics, two A genome regions are compared with their B genome homeologues.

Key Results

BAC-FISH using 27 A. duranensis BAC clones as probes gave dispersed and repetitive DNA characteristic signals, predominantly in interstitial regions of the peanut A chromosomes. The sequences of 14 BAC clones showed complete and truncated copies of ten abundant long terminal repeat (LTR) retrotransposons, characterized here. Almost all dateable transposition events occurred <3·5 million years ago, the estimated date of the divergence of A and B genomes. The most abundant retrotransposon is Feral, apparently parasitic on the retrotransposon FIDEL, followed by Pipa, also non-autonomous and probably parasitic on a retrotransposon we named Pipoka. The comparison of the A and B genome homeologous regions showed conserved segments of high sequence identity, punctuated by predominantly indel regions without significant similarity.

Conclusions

A substantial proportion of the highly repetitive component of the peanut A genome appears to be accounted for by relatively few LTR retrotransposons and their truncated copies or solo LTRs. The most abundant of the retrotransposons are non-autonomous. The activity of these retrotransposons has been a very significant driver of genome evolution since the evolutionary divergence of the A and B genomes.     

Mapping quantitative trait loci (QTL) in sheep. IV. Analysis of lactation persistency and extended lactation traits in sheep

Background

In sheep dairy production, total lactation performance, and length of lactation of lactation are of economic significance. A more persistent lactation has been associated with improved udder health. An extended lactation is defined by a longer period of milkability. This study is the first investigation to examine the presence of quantitative trait loci (QTL) for extended lactation and lactation persistency in sheep.

Methods

An (Awassi × Merino) × Merino single-sire backcross family with 172 ewes was used to map QTL for lactation persistency and extended lactation traits on a framework map of 189 loci across all autosomes. The Wood model was fitted to data from multiple lactations to estimate parameters of ovine lactation curves, and these estimates were used to derive measures of lactation persistency and extended lactation traits of milk, protein, fat, lactose, useful yield, and somatic cell score. These derived traits were subjected to QTL analyses using maximum likelihood estimation and regression analysis.

Results

Overall, one highly significant (LOD > 3.0), four significant (2.0 < LOD < 3.0) and five suggestive (1.7 < LOD < 2.0) QTL were detected across all traits in common by both mapping methods. One additional suggestive QTL was identified using maximum likelihood estimation, and four suggestive (0.01 < P < 0.05) and two significant (P < 0.01) QTL using the regression approach only. All detected QTL had effect sizes in the range of 0.48 to 0.64 SD, corresponding to QTL heritabilities of 3.1 to 8.9%. The comparison of the detected QTL with results in cattle showed conserved linkage regions. Most of the QTL identified for lactation persistency and extended lactation did not coincide. This suggests that persistency and extended lactation for the same as well as different milk yield and component traits are not controlled by the same genes.

Conclusion

This study identified ten novel QTL for lactation persistency and extended lactation in sheep, but results suggest that lactation persistency and extended lactation do not have a major gene in common. These results provide a basis for further validation in extended families and other breeds as well as targeting regions for genome-wide association mapping using high-density SNP arrays.     

Somatic hybrid plants of Nicotiana x sanderae (+) N. debneyi with fungal resistance to Peronospora tabacina

Background and Aims

The genus Nicotiana includes diploid and tetraploid species, with complementary ecological, agronomic and commercial characteristics. The species are of economic value for tobacco, as ornamentals, and for secondary plant-product biosynthesis. They show substantial differences in disease resistance because of their range of secondary products. In the last decade, sexual hybridization and transgenic technologies have tended to eclipse protoplast fusion for gene transfer. Somatic hybridization was exploited in the present investigation to generate a new hybrid combination involving two sexually incompatible tetraploid species. The somatic hybrid plants were characterized using molecular, molecular cytogenetic and phenotypic approaches.

Methods

Mesophyll protoplasts of the wild fungus-resistant species N. debneyi (2n = 4x = 48) were electrofused with those of the ornamental interspecific sexual hybrid N. × sanderae (2n = 2x = 18). From 1570 protoplast-derived cell colonies selected manually in five experiments, 580 tissues were sub-cultured to shoot regeneration medium. Regenerated plants were transferred to the glasshouse and screened for their morphology, chromosomal composition and disease resistance.

Key Results

Eighty-nine regenerated plants flowered; five were confirmed as somatic hybrids by their intermediate morphology compared with parental plants, cytological constitution and DNA-marker analysis. Somatic hybrid plants had chromosome complements of 60 or 62. Chromosomes were identified to parental genomes by genomic in situ hybridization and included all 18 chromosomes from N. × sanderae, and 42 or 44 chromosomes from N. debneyi. Four or six chromosomes of one ancestral genome of N. debneyi were eliminated during culture of electrofusion-treated protoplasts and plant regeneration. Both chloroplasts and mitochondria of the somatic hybrid plants were probably derived from N. debneyi. All somatic hybrid plants were fertile. In contrast to parental plants of N. × sanderae, the seed progeny of somatic hybrid plants were resistant to infection by Peronospora tabacina, a trait introgressed from the wild parent, N. debneyi.

Conclusions

Sexual incompatibility between N. × sanderae and N. debneyi was circumvented by somatic hybridization involving protoplast fusion. Asymmetrical nuclear hybridity was seen in the hybrids with loss of chromosomes, although importantly, somatic hybrids were fertile and stable. Expression of fungal resistance makes these somatic hybrids extremely valuable germplasm in future breeding programmes in ornamental tobacco.     

Synthesis of a Nano-Silver Metal Ink for Use in Thick Conductive Film Fabrication Applied on a Semiconductor Package

The success of printing technology in the electronics industry primarily depends on the availability of metal printing ink. Various types of commercially available metal ink are widely used in different industries such as the solar cell, radio frequency identification (RFID) and light emitting diode (LED) industries, with limited usage in semiconductor packaging. The use of printed ink in semiconductor IC packaging is limited by several factors such as poor electrical performance and mechanical strength. Poor adhesion of the printed metal track to the epoxy molding compound is another critical factor that has caused a decline in interest in the application of printing technology to the semiconductor industry. In this study, two different groups of adhesion promoters, based on metal and polymer groups, were used to promote adhesion between the printed ink and the epoxy molding substrate. The experimental data show that silver ink with a metal oxide adhesion promoter adheres better than silver ink with a polymer adhesion promoter. This result can be explained by the hydroxyl bonding between the metal oxide promoter and the silane grouping agent on the epoxy substrate, which contributes a greater adhesion strength compared to the polymer adhesion promoter. Hypotheses of the physical and chemical functions of both adhesion promoters are described in detail.     

Planning for remodelling: nuclear architecture,chromatin and chromosomes

DNA sequences occupy three-dimensional positions and their architecture is related to gene expression, gene-protein interactions and epigenetic processes. The recent analysis of chromosome 4 in Arabidopsis interphase nuclei reveals that gene-rich, undermethylated DNA is composed of active loops of 200 to 2000 kb associated with acetylated histones, providing a well-defined model system to study chromatin in its nuclear context.     

Evolutionary design principles and functional characteristics based on kingdom-specific network motifs

BACKGROUND: Network motifs within biological networks show non-random abundances in systems at different scales. Large directed protein networks at the cellular level are now well defined in several diverse species. We aimed to compare the nature of significantly observed two- and three-node network motifs across three different kingdoms (Arabidopsis thaliana for multicellular plants, Saccharomyces cerevisiae for unicellular fungi and Homo sapiens for animals). RESULTS: 'Two-node feedback' is the most significant motif in all three species. By considering the sign of each two-node feedback interaction, we examined the enrichment of the three types of two-node feedbacks [positive-positive (PP), negative-negative (NN) and positive-negative (PN)]. We found that PN is enriched in the network of A.thaliana, NN in the network of S.cerevisiae and PP and NN in the network of H.sapiens. Each feedback type has characteristic features of robustness, multistability and homeostasis. Conclusions: We suggest that amplification of particular network motifs emerges from contrasting dynamical and topological properties of the motifs, reflects the evolutionary design principles selected by the characteristic behavior of each species and provides a signature pointing to their behavior and function.