Transmitting tissue architecture in basal-relictual angiosperms: Implications for transmitting tissue origins

Carpel transmitting tissue is a major floral innovation that is essential for angiosperm success. It facilitates the rapid adhesion, hydration, and growth of the male gametophyte to the female gametophyte. As well, it functions as a molecular screen to promote male gametophytic competition and species-specific recognition and compatibility. Here, we characterize the transmitting tissue extracellular matrix (ECM) and pollen tube growth in basal-relictual angiosperms and test the hypothesis that a freely flowing ECM (wet stigma) was ancestral to a cuticle-bound ECM (dry stigma). We demonstrate that the most recent common ancestor of extant angiosperms produced an ECM that was structurally and functionally equivalent to a dry stigma. Dry stigmas are composed of a cuticle and primary wall that contains compounds that facilitate the adhesion and growth of the male gametophyte. These compounds include methyl-esterified homogalacturonans, arabinogalactan-proteins, and lipids. We propose that transmitting tissue evolved in concert with an increase in cuticle permeability that resulted from modifications in the biosynthesis and secretion of fatty acids needed for cuticle construction. Increased cuticle permeability exposed the male gametophyte to pre-existing molecules that enabled rapid male gametophyte adhesion, hydration, and growth as well as species-specific recognition and compatibility.     

Impact of Chikungunya Virus Infection on Health Status and Quality of Life: A Retrospective Cohort Study

Background

Persistent symptoms, mainly joint and muscular pain and depression, have been reported several months after Chikungunya virus (CHIKV) infection. Their frequency and their impact on quality of life have not been compared with those of an unexposed population. In the present study, we aimed to describe the frequency of prolonged clinical manifestations of CHIKV infection and to measure the impact on quality of life and health care consumption in comparison with that of an unexposed population, more than one year after infection.

Methodology/Principal Findings

In a retrospective cohort study, 199 subjects who had serologically confirmed CHIKV infection (CHIK+) were compared with 199 sero-negative subjects (CHIK–) matched for age, gender and area of residence in La Réunion Island. Following an average time of 17 months from the acute phase of infection, participants were interviewed by telephone about current symptoms, medical consumption during the last 12 months and quality of life assessed by the 12-items Short-Form Health Survey (SF-12) scale. At the time of study, 112 (56%) CHIK+ persons reported they were fully recovered. CHIK+ complained more frequently than CHIK– of arthralgia (relative risk = 1.9; 95% confidence interval: 1.6–2.2), myalgia (1.9; 1.5–2.3), fatigue (2.3; 1.8–3), depression (2.5; 1.5–4.1) and hair loss (3.8; 1.9–7.6). There was no significant difference between CHIK+ and CHIK– subjects regarding medical consumption in the past year. The mean (SD) score of the SF-12 Physical Component Summary was 46.4 (10.8) in CHIK+ versus 49.1 (9.3) in CHIK– (p = 0.04). There was no significant difference between the two groups for the Mental Component Summary.

Conclusions/Significance

More than one year following the acute phase of infection, CHIK+ subjects reported more disabilities than those who were CHIK–. These persistent disabilities, however, have no significant influence on medical consumption, and the impact on quality of life is moderate.     

A human genome structural variation sequencing resource reveals insights into mutational mechanisms

Understanding the prevailing mutational mechanisms responsible for human genome structural variation requires uniformity in the discovery of allelic variants and precision in terms of breakpoint delineation. We develop a resource based on capillary end sequencing of 13.8 million fosmid clones from 17 human genomes and characterize the complete sequence of 1054 large structural variants corresponding to 589 deletions, 384 insertions, and 81 inversions. We analyze the 2081 breakpoint junctions and infer potential mechanism of origin. Three mechanisms account for the bulk of germline structural variation: microhomology-mediated processes involving short (2-20 bp) stretches of sequence (28%), nonallelic homologous recombination (22%), and L1 retrotransposition (19%). The high quality and long-range continuity of the sequence reveals more complex mutational mechanisms, including repeat-mediated inversions and gene conversion, that are most often missed by other methods, such as comparative genomic hybridization, single nucleotide polymorphism microarrays, and next-generation sequencing.     

"Ring pledget": a new concept for secure apex closure during transapical aortic valve implantation

Transapical aortic valve implantation requires puncture of the left ventricle apex and insertion of a 32-French delivery sheath. A critical step in the procedure consists of secure closure of the ventricular apex. We describe 2 cases of apical rupture of 42 transapical aortic valve implantations. Furthermore, we describe the use of a newly designed single circular Teflon pledget that can help to avoid this complication. This pledget provides a more secure and uniform shrinkage of the entire apex to close the defect left by the delivery sheath.     

Extracellular production of Streptomyces lividans acetyl xylan esterase A in Escherichia coli for rapid detection of activity

Acetyl xylan esterase A (AxeA) from Streptomyces lividans belongs to a large family of industrially relevant polysaccharide esterases. AxeA and its truncated form containing only the catalytically competent domain, AxeA(tr), catalyze both the deacetylation of xylan and the N-deacetylation of chitosan. This broad substrate specificity lends additional interest to their characterization and production. Here, we report three systems for extracellular production of AxeA(tr): secretion from the native host S. lividans with the native signal peptide, extracellular production in Escherichia coli with the native signal peptide, and in E. coli with the OmpA signal peptide. Over five to seven days of a shake flask culture, the native host S. lividans with the native signal peptide secreted AxeA(tr) into the extracellular medium in high yield (388 mg/L) with specific activity of 19 U/mg corresponding to a total of 7000 U/L. Over one day of shake flask culture, E. coli with the native secretion signal peptide produced 84-fold less in the extracellular medium (4.6 mg/L), but the specific activity was higher (100 U/mg) corresponding to a total of 460 U/L. A similar E. coli culture using the OmpA signal peptide, produced 10mg/L with a specific activity of 68 U/mg, corresponding to a total of 680 U/L. In 96-well microtiter plates, extracellular production with E. coli gave approximately 30 and approximately 86 microg/mL in S. lividans. Expression in S. lividans with the native signal peptide is best for high level production, while expression in E. coli using the OmpA secretion signal peptide is best for high-throughput expression and screening of variants in microtiter plate format.     

Nectar-carbohydrate production and composition vary in relation to nectary anatomy and location within individual flowers of several species of Brassicaceae

Nectar-carbohydrate production and composition were investigated by high-performance liquid chromatography and enzymology in nine species from five tribes of the Brassicaceae. In six species (Arabidopsis thaliana (L.) Heynh., Brassica napus L., B. rapa L., Lobularia maritima (L.) Desv., Raphanus sativus L., Sinapis arvensis L.) that produced nectar from both lateral nectaries (associated with the short stamens) and median nectaries (outside the long stamens), on average 95% of the total nectar carbohydrate was collected from the lateral ones. Nectar from these glands possessed a higher glucose/fructose ratio (usually 1.0–1.2) than that from the median nectaries (0.2–0.9) within the same flower. Comparatively little sucrose was detected in any nectar samples except from Matthiola bicornus (Sibth. et Sm.) DC., which possessed lateral nectaries only and produced a sucrose-dominant exudate. The anatomy of the nectarial tissue in nectar-secreting flowers of six species, Hesperis matronalis L., L. maritima, M. bicornus, R. sativus, S. arvensis, and Sisymbrium loeselii L., was studied by light and scanning-electron microscopy. Phloem alone supplied the nectaries. However, in accordance with their overall nectar-carbohydrate production, the lateral glands received relatively rich quantities of phloem that penetrated far into the glandular tissue, whereas median glands were supplied with phloem that often barely innervated them. All nectarial tissue possessed modified stomata (with the exception of the median glands of S. loeselii, which did not produce nectar); further evidence was gathered to indicate that these structures do not regulate nectar flow by guard-cell movements. The numbers of modified stomata per gland showed no relation to nectar-carbohydrate production. Taken together, the data on nectar biochemistry and nectary anatomy indicate the existence of two distinct nectary types in those Brassicacean species that possess both lateral and median nectaries, regardless of whether nectarial tissue is united around the entire receptacle or not. It is proposed that the term “nectarium” be used to represent collectively the multiple nectaries that can be found in individual flowers. Received: 21 July 1997 / Accepted: 19 September 1997     

Spatial effects and rare outcrossing events in Medicago truncatula (Fabaceae)

In order to elucidate the mechanisms underlying the large amount of RAPD polymorphism found in 1990 in a population of the selfing annual Medicago truncatula GAERTN. (Fabaceae), we have analysed most of the individuals (n = 363) from the same population 6 years later using microsatellite loci. We confirm the result of the earlier study, namely that this population is very polymorphic and highly subdivided, with approximately 37% of the variance distributed among subpopulations, only 50 m apart one from another. We use standard F-statistics analyses, linkage disequilibria, minimum spanning network, multilocus assignment tests and spatial autocorrelation analyses to test the hypotheses that spatial structure and outcrossing events are involved in maintaining the large amount of genetic diversity at the level of each subpopulation. Interestingly, fine-scale spatial structure could be observed in only one subpopulation suggesting that other mechanisms are acting elsewhere. To the best of our knowledge, this is the first study of fine spatial genetic structure in a predominantly selfing species.     

Isolation and Characterization of a New Peroxiredoxin from Poplar Sieve Tubes That Uses Either Glutaredoxin or Thioredoxin as a Proton Donor

A sequence coding for a peroxiredoxin (Prx) was isolated from a xylem/phloem cDNA library from Populus trichocarpa and subsequently inserted into an expression plasmid yielding the construction pET-Prx. The recombinant protein was produced in Escherichia coli cells and purified to homogeneity with a high yield. The poplar Prx is composed of 162 residues, a property that makes it the shortest plant Prx sequence isolated so far. It was shown that the protein is monomeric and possesses two conserved cysteines (Cys). The Prx degrades hydrogen peroxide and alkyl hydroperoxides in the presence of an exogenous proton donor that can be either thioredoxin or glutaredoxin (Grx). Based on this finding, we propose that the poplar protein represents a new type of Prx that differs from the so-called 2-Cys and 1-Cys Prx, a suggestion supported by the existence of natural fusion sequences constituted of a Prx motif coupled to a Grx motif. The protein was shown to be highly expressed in sieve tubes where thioredoxin h and Grx are also major proteins.     

Pyruvate kinase isozymes in man

Anti human M2 type and anti human L type pyruvate kinase sera allowed us to distinguish two groups of pyruvate kinase in man. Erythrocyte and liver (L type) enzymes on the one hand were inhibited by anti L and not all by anti M2 serum; pyruvate kinase from all the other tissues on the other hand were inhibited by anti M2 and not at all by anti L serum. This latter group represent the M type pyruvate kinase isozymes. The M type isozymes have been studied by electrofocusing in thin layer acrylamide-ampholine gel. In adult tissues 4 types of isozymes were found, designated, from acid to alkaline pH, as M2 (predominant form in spleen, leukocytes, lung...), M3, M4 and M1 (predominant form in muscle and brain). In foetal tissues an extra band M2, called M2f, more anodic than M2, was added to the previously described isozymes. Except in brain (in which the isozymes M2, M3, M4 and M1 were found), the most anodic bands (M2f, M2 and M3) were predominant in all the foetal tissues. The isozymes M2f and M2 seem therefore to be the original M type pyruvate kinase forms from which the other isozymes issue. The rate of each isozyme seems to depend on tissue factors characterizing the state of differentiation of some tissues, as indicated by the ability of adult muscle extracts to change the isozymes M2 and M3 into more cathodic forms.