Nuclear DNA Amounts in Angiosperms and their Modern Uses--807 New Estimates

The DNA amount in the unreplicated haploid nucleus of an organismis known as its C-value. C-values differ about 1000-fold amongangiosperms and are characteristic of taxa. The data are usedin many biological fields, so they should be easily available.Values for 2802 angiosperm species (1%) were estimated during1950–1997, and five collected lists of C-values were publishedfor reference purposes during 1976–1997. Numbers of newangiosperm C-values published recently remained high, necessitatinga further supplementary list. This paper lists DNA C-valuesfor 807 angiosperm species from 70 original sources, including520 (75.2%) from sources published after 1996, and 691 for speciesnot included in any of the previous five lists. There is a continuingneed to estimate accurate DNA C-values for plant taxa, as shownin a workshop on this biodiversity topic sponsored by Annalsof Botany and held at Kew in 1997. Its key aim was to identifymajor gaps in our knowledge of plant DNA amounts and to recommendtargets and priorities for new work to fill them. A target ofestimating first C-values for the next 1% of angiosperm speciesin 5 years was set. The proportion of such C-values in the presentwork (85.6%) is very high; and the number being published (approx.220 per annum) has never been exceeded. In 1997, C-values werestill unknown for most (68%) families, so a target of completecoverage was set. This paper includes first C-values for 12families, but as less than 2% of such values listed here targetednew families, the need to improve familial representation remains.Copyright 2000 Annals of Botany Company Angiosperm DNA amounts, DNA C-values, nuclear genome sizes, plant DNA database     

Efficient GA3-assisted plant regeneration from cell suspensions of three grape genotypes via somatic embryogenesis

Petioles from in vitro grown plants of interspecific grapevine hybrids cvs `Bianca', `Podarok Magaracha' and `Intervitis Magaracha' were cultured on solid NN medium supplemented with 2,4-D and BA at various concentrations. The callus developed was cultured in liquid NN medium supplemented with 0.5 mg l<sup>–1</sup> BA to induce formation of somatic embryos. Somatic embryos of globular and heart-stage developed in suspensions of `Podarok Magaracha' and `Intervitis Magaracha'. In contrast, `Bianca' did not undergo embryogenesis beyond globular stage. This made it necessary to perform subculture of the suspensions to HTE liquid medium supplemented with 0.2 mg l^–1 BA for the development of globular embryos into heart stage. Heart-stage embryos developed into torpedo-stage after subculturing suspensions of all three cultivars to liquid HTE medium supplemented with 0.1 mg l^–1 IAA and 30 mg l^–1 sodium hummate. Torpedo-stage embryo suspensions were subcultured in liquid HTE medium supplemented with 0.5 mg l^–1 BA, 0.5 mg l^–1 GA₃ and 0.5 mg l^–1 GA₃ + 0.2 mg l^–1 BA. After 12 days of incubation, plantlets were cultured on solid M2MS medium: without growth regulators and with 0.5 mg l^–1 BA. Plantlets that developed in liquid HTE media with 0.5 mg l^–1 GA₃ or 0.5 mg l^–1 GA₃ + 0.2 mg l^–1 BA produced 82–90% shoots on solid M2MS medium with 0.5 mg l^–1 BA after 50 days of culture.     

Acuity of a Cryptochrome and Vision-Based Magnetoreception System in Birds

The magnetic compass of birds is embedded in the visual system and it has been hypothesized that the primary sensory mechanism is based on a radical pair reaction. Previous models of magnetoreception have assumed that the radical pair-forming molecules are rigidly fixed in space, and this assumption has been a major objection to the suggested hypothesis. In this article, we investigate theoretically how much disorder is permitted for the radical pair-forming, protein-based magnetic compass in the eye to remain functional. Our study shows that only one rotational degree of freedom of the radical pair-forming protein needs to be partially constrained, while the other two rotational degrees of freedom do not impact the magnetoreceptive properties of the protein. The result implies that any membrane-associated protein is sufficiently restricted in its motion to function as a radical pair-based magnetoreceptor. We relate our theoretical findings to the cryptochromes, currently considered the likeliest candidate to furnish radical pair-based magnetoreception.     

Genesis of tramsmissible protein states via deformed templating

Prion replication occurs via a template-assisted mechanism, which postulates that the folding pattern of a newly recruited polypeptide chain accurately reproduces that of a template. The concept of prion-like template-assisted propagation of an abnormal protein conformation has been expanded to amyloidogenic proteins associated with Alzheimer, Parkinson, Huntington diseases, amyotrophic lateral sclerosis and others. Recent studies demonstrated that authentic PrP^Sc and transmissible prion disease could be generated in wild type animals by inoculation of recombinant prion protein amyloid fibrils, which are structurally different from PrP^Sc and lack any detectable PrP^Sc particles. Here we discuss a new replication mechanism designated as “deformed templating,” according to which fibrils with one cross-β folding pattern can seed formation of fibrils or particles with a fundamentally different cross-β folding pattern. Transformation of cross-β folding pattern via deformed templating provides a mechanistic explanation behind genesis of transmissible protein states induced by amyloid fibrils that are considered to be non-infectious. We postulate that deformed templating is responsible for generating conformationally diverse amyloid populations, from which conformers that are fit to replicate in a particular cellular environment are selected. We propose that deformed templating represents an essential step in the evolution of transmissible protein states.     

Sphingomyelin synthesis in Ascaridia galli

Adult Ascaridia galli incorporate label from [U-¹⁴C] serine into various intermediates of sphingomyelin synthesis (ketosphinganine, sphinganine, sphingosine, ceramide and sphingomyelin). From the results it is concluded that A. galli possesses the five enzymes involved in sphingomyelin synthesis, namely: serine palmitoyltransferase, 3-ketosphinganine reductase, flavoprotein sphinganine reductase, sphingosine acyltransferase and ceramide choline phosphotransferase.     

Bicoid gradient formation mechanism and dynamics revealed by protein lifetime analysis

Embryogenesis relies on instructions provided by spatially organized signaling molecules known as morphogens. Understanding the principles behind morphogen distribution and how cells interpret locally this information remains a major challenge in developmental biology. Here, we introduce morphogen‐age measurements as a novel approach to test models of morphogen gradient formation. Using a tandem fluorescent timer as a protein age sensor, we find a gradient of increasing age of Bicoid along the anterior–posterior axis in the early Drosophila embryo. Quantitative analysis of the protein age distribution across the embryo reveals that the synthesis–diffusion–degradation model is the most likely model underlying Bicoid gradient formation, and rules out other hypotheses for gradient formation. Moreover, we show that the timer can detect transitions in the dynamics associated with syncytial cellularization. Our results provide new insight into Bicoid gradient formation and demonstrate how morphogen‐age information can complement knowledge about movement, abundance, and distribution, which should be widely applicable to other systems.     

Persistence,dispersal and genetic evolution of recently formed <Emphasis Type="Italic">Spartina</Emphasis> homoploid hybrids and allopolyploids in Southern England

In Southampton Water, UK, the recent (c. 150 years ago) interspecific hybridisation between Spartina alterniflora (2n = 6x = 62; A-genome) and S. maritima (2n = 6x = 60; M-genome) gave rise to the homoploid hybrid (S. × townsendii, 2n = 6x = 62), and subsequently to the invasive allododecaploid species S. anglica (2n = 12x = 120–124) that has since spread worldwide. To address the question of dynamics of mixed ploidy populations involving these plants, we analysed several Spartina populations (fifty one individuals) in Southern England, UK, one of which was the presumed place of origin of the homoploid hybrid (Hythe). Using a combination of flow cytometry and ribosomal DNA (rDNA) genotyping we were able to identify the genomic composition and ploidy level of each individual analysed. The data show that the homoploid hybrid still dominates the population at Hythe (82 % of individuals collected in that locality) since its origin in the nineteenth century. We also identified S. × townsendii for the first time on Hayling Island (66 % individuals), indicating dispersal beyond its likely origin. The fertile allododecaploid S. anglica was mainly found in populations outside the initial hybridisation site, on Hayling Island and at Eling Marchwood. Quantification of the rDNA contributions from each parental genome showed that the ratios were mostly balanced in S. × townsendii. However, two (3 %) S. anglica individuals analysed have lost nearly all M-genome homeologs, indicating extensive repeat loss. Such variation indicates that despite the presumed single allopolyploid origin of S. anglica and genetic uniformity at other loci, it has undergone substantial changes at the rDNA loci following genome duplication.     

Bioengineering and functional characterization of arenicin shortened analogs with enhanced antibacterial activity and cell selectivity

New bioengineering approaches are required for development of more active and less toxic antimicrobial peptides. In this study we used β‐hairpin antimicrobial peptide arenicin‐1 as a template for design of more potent antimicrobials. In particular, six shortened 17‐residue analogs were obtained by recombinant expression in Escherichia coli. Besides, we have introduced the second disulfide bridge by analogy with the structure of tachyplesins. As a result, a number of analogs with enhanced activity and cell selectivity were developed. In comparison with arenicin‐1, which acts on cell membranes with low selectivity, the most potent and promising its analog termed ALP1 possessed two‐fold higher antibacterial activity and did not affect viability of mammalian cells at concentration up to 50 μM. The therapeutic index of ALP1 against both Gram‐positive and Gram‐negative bacteria was significantly increased compared with that of arenicin‐1 while the mechanism of action remained the same. Like arenicin‐1, the analog rapidly disrupt membranes of both stationary and exponential phase bacterial cells and effectively kills multidrug‐resistant Gram‐negative bacteria. Furthermore, ALP1 was shown to bind DNA in vitro at a ratio of 1:1 (w/w). The circular dichroism spectra demonstrated that secondary structures of the shortened analogs were similar to that of arenicin‐1 in water solution, but significantly differed in membrane‐mimicking environments. This work shows that a strand length is one of the key parameters affecting cell selectivity of β‐hairpin antimicrobial peptides. Copyright © 2015 European Peptide Society and John Wiley & Sons, Ltd.