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International audience; Cyclic di-AMP is an essential signaling molecule in Gram-positive bacteria. This second messenger regulates the osmotic pressure of the cell by interacting directly with the regulatory domains, either RCK_C or CBS domains, of several potassium and osmolyte uptake membrane protein systems. Cyclic di-AMP also targets stand-alone CBS domain proteins such as DarB in Bacillus subtilis and CbpB in Listeria monocytogenes. We show here that the CbpB protein of Group B Streptococcus binds c-di-AMP with a very high affinity. Crystal structures of CbpB reveal the determinants of binding specificity and significant conformational changes occurring upon c-di-AMP binding. Deletion of the cbpB gene alters bacterial growth in low potassium conditions most likely due to a decrease in the amount of ppGpp caused by a loss of interaction between CbpB and Rel, the GTP/GDP pyrophosphokinase.

Maternal group B Streptococcus (GBS) colonization is a major risk factor for neonatal GBS infection. However, data on GBS are scarce in low- and middle-income countries. Using sociodemographic data and vaginal swabs collected from an international cohort of mothers and newborns, this study aimed to estimate the prevalence of GBS colonization among pregnant women in Madagascar (n = 1,603) and Senegal (n = 616). The prevalence was 5.0% (95% CI, 3.9–6.1) and 16.1% (95% CI, 13.1–19.0) in Madagascar and Senegal, respectively. No factors among sociodemographic characteristics, living conditions, and obstetric history were found to be associated independently with GBS colonization in both countries. This community-based study provides one of the first estimates of maternal GBS colonization among pregnant women from Madagascar and Senegal.

Above-optimal temperatures reduce yield in many crops, including tomato, largely because of the heat-sensitivity of their reproduction process. A full understanding of heat-stress (HS) response and thermotolerance of tomato reproduction is still lacking. Recently, using external application of the plant hormone ethylene, it was demonstrated that ethylene plays a role in heat-tolerance of tomato pollen (the male reproductive cells). In order to expand our understanding on involvement of ethylene in tomato pollen thermotolerance, we analyzed the response of wild type and ethylene-related tomato mutant plants to HS, at physiological and molecular levels. We report that mild chronic HS conditions highly reduce the number of viable and germinating pollen grains as well as the production of seeded fruits in wild type tomato plants, while no significant reduction was detected/observed in pollen quality, number of seeded fruits and seeds per fruit in plants of the ethylene over-producer mutant epinastic. Our findings suggest that ethylene is involved in thermotolerance of tomato reproduction, pointing to an effect on pollen viability and germination potential, highlighting candidate genes involved in pollen response to HS (like SlHSP17, SlHSP101, SlMBF1) and suggesting directions for further studies.

Group B Streptococcus (GBS) is a Gram-positive bacterium able to switch from a harmless commensal of healthy adults to a pathogen responsible for invasive infections in neonates. The signals and regulatory mechanisms governing this transition are still largely unknown. CodY is a highly conserved global transcriptional regulator that links nutrient availability to the regulation of major metabolic and virulence pathways in low-G+C Gram-positive bacteria. In this work, we investigated the role of CodY in BM110, a GBS strain representative of a hypervirulent lineage associated with the majority of neonatal meningitis. Deletion of codY resulted in a reduced ability of the mutant strain to cause infections in neonatal and adult animal models. The observed decreased in vivo lethality was associated with an impaired ability of the mutant to persist in the blood, spread to distant organs, and cross the blood-brain barrier. Notably, the codY null mutant showed reduced adhesion to monolayers of human epithelial cells in vitro and an increased ability to form biofilms, a phenotype associated with strains able to asymptomatically colonize the host. RNA-seq analysis showed that CodY controls about 13% of the genome of GBS, acting mainly as a repressor of genes involved in amino acid transport and metabolism and encoding surface anchored proteins, including the virulence factor Srr2. CodY activity was shown to be dependent on the availability of branched-chain amino acids, which are the universal cofactors of this regulator. These results highlight a key role for CodY in the control of GBS virulence.

Group B

Virulence of the neonatal pathogen Group B Streptococcus depends on the master regulator CovR. Inactivation of CovR leads to large-scale transcriptome remodeling and impairs almost every step of the interaction between the pathogen and the host. However, comparative analyses suggested a plasticity of the CovR signalling pathway in clinical isolates, probably due to the host selective pressure and leading to phenotypic heterogeneity in the bacterial population. Here, we characterize the CovR regulatory network in a strain representative of the hypervirulent lineage responsible of the majority of late-onset meningitidis. Genome-wide binding and transcriptome analysis demonstrated that CovR acts as a direct and global repressor of virulence genes, either as a primary regulator or with specialized co-regulators. Remarkably, CovR directly regulates genes of the pan-genome, including the two specific hypervirulent adhesins and horizontally acquired genes, as well as core-genes showing mutational biases in the population. Parallel analysis of the CovR network in a second isolate links strain-specificities to micro-evolutions in CovR-regulated promoters and to broad difference due to variability in CovR activation by phosphorylation. Our results highlight the direct, coordinated, and strain-specific regulation of virulence genes by CovR. This intra-species evolution of the signalling network reshapes bacterial-host interactions, increasing the potential for adaptation and the emergence of clone associated with specific diseases.

International audience; Binding of microbial pathogens to host vitronectin (Vtn) is a common theme in the pathogenesis of invasive infections. In this study, we characterized the role of Vtn in the invasion of mucosal epithelial cells by Streptococcus agalactiae (i.e. group B streptococcus or GBS), a frequent human pathogen. Moreover, we identified PbsP, a previously described plasminogen-binding protein of GBS, as a dual adhesin that can also interact with human Vtn through its streptococcal surface repeat (SSURE) domains. Deletion of the pbsP gene decreases both bacterial adhesion to Vtn-coated inert surfaces and the ability of GBS to interact with epithelial cells. Bacterial adherence to and invasion of epithelial cells were either inhibited or enhanced by cell pretreatment with, respectively, anti-Vtn antibodies or Vtn, confirming the role of Vtn as a GBS ligand on host cells. Finally, antibodies directed against the integrin αv subunit inhibited Vtn-dependent cell invasion by GBS. Collectively, these results indicate that Vtn acts as a bridge between the SSURE domains of PbsP on the GBS surface and host integrins to promote bacterial invasion of epithelial cells. Therefore, inhibition of interactions between PbsP and extracellular matrix components could represent a viable strategy to prevent colonization and invasive disease by GBS.

Tomato pollen grains have the capacity for ethylene production, possessing specific components of the ethylene-biosynthesis and -signaling pathways, being affected/responsive to high-temperature conditions. Exposure of plants to heat stress (HS) conditions reduces crop yield and quality, mainly due to sensitivity of pollen grains. Recently, it was demonstrated that ethylene, a gaseous plant hormone, plays a significant role in tomato pollen heat-tolerance. It is not clear, however, whether, or to what extent, pollen grains are dependent on the capacity of the surrounding anther tissues for ethylene synthesis and signaling, or can synthesize this hormone and possess an active signaling pathway. The aim of this work was (1) to investigate if isolated, maturing and mature, tomato pollen grains have the capacity for ethylene production, (2) to find out whether pollen grains possess an active ethylene-biosynthesis and -signaling pathway and characterize the respective tomato pollen components at the transcript level, (3) to look into the effect of short-term HS conditions. Results from accumulation studies showed that pollen, anthers, and flowers produced ethylene and HS affected differentially ethylene production by (rehydrated) mature pollen, compared to anthers and flowers, causing elevated ethylene levels. Furthermore, several ethylene synthesis genes were expressed, with SlACS3 and SlACS11 standing out as highly HS-induced genes of the pollen ethylene biosynthesis pathway. Specific components of the ethylene-signaling pathway as well as several ethylene-responsive factors were expressed in pollen, with SlETR3 (ethylene receptor; named also NR, for never ripe) and SlCTR2 (constitutive triple response2) being HS responsive. This work shows that tomato pollen grains have the capacity for ethylene production, possessing active ethylene-biosynthesis and -signaling pathways, highlighting specific pollen components that serve as a valuable resource for future research on the role of ethylene in pollen thermotolerance.

Cyclic nucleotides are universally used as secondary messengers to control cellular physiology. Among these signalling molecules, cyclic di-adenosine monophosphate (c-di-AMP) is a specific bacterial second messenger recognized by host cells during infections and its synthesis is assumed to be necessary for bacterial growth by controlling a conserved and essential cellular function. In this study, we sought to identify the main c-di-AMP dependent pathway in Streptococcus agalactiae, the etiological agent of neonatal septicaemia and meningitis. By conditionally inactivating dacA, the only diadenyate cyclase gene, we confirm that c-di-AMP synthesis is essential in standard growth conditions. However, c-di-AMP synthesis becomes rapidly dispensable due to the accumulation of compensatory mutations. We identified several mutations restoring the viability of a ΔdacA mutant, in particular a loss-of-function mutation in the osmoprotectant transporter BusAB. Identification of c-di-AMP binding proteins revealed a conserved set of potassium and osmolyte transporters, as well as the BusR transcriptional factor. We showed that BusR negatively regulates busAB transcription by direct binding to the busAB promoter. Loss of BusR repression leads to a toxic busAB expression in absence of c-di-AMP if osmoprotectants, such as glycine betaine, are present in the medium. In contrast, deletion of the gdpP c-di-AMP phosphodiesterase leads to hyperosmotic susceptibility, a phenotype dependent on a functional BusR. Taken together, we demonstrate that c-di-AMP is essential for osmotic homeostasis and that the predominant mechanism is dependent on the c-di-AMP binding transcriptional factor BusR. The regulation of osmotic homeostasis is likely the conserved and essential function of c-di-AMP, but each species has evolved specific c-di-AMP mechanisms of osmoregulation to adapt to its environment., Author summary Nucleotide-based second messengers play central functions in bacterial physiology and host-pathogen interactions. Among these signalling nucleotides, cyclic-di-AMP (c-di-AMP) synthesis was originally assumed to be essential for bacterial growth. In this study, we confirmed that the only di-adenylate cyclase enzyme in the opportunistic pathogen Streptococcus agalactiae is essential in standard growth conditions. However, c-di-AMP synthesis becomes rapidly dispensable by accumulating spontaneous mutations in genes involved in osmotic regulation. We identified that c-di-AMP binds directly to four proteins necessary to maintain osmotic homeostasis, including three osmolyte transporters and the BusR transcriptional factor. We demonstrated that BusR negatively controls the expression of the busAB operon and that it is the main component leading to growth inhibition in the absence of c-di-AMP synthesis if osmoprotectants are present in the environment. Overall, c-di-AMP is essential to maintain osmotic homeostasis by coordinating osmolyte uptake and thus bacteria have developed specific mechanisms to keep c-di-AMP as the central regulator of osmotic homeostasis.

Pollen development at high temperature depends on a fine balance between acclimation and injury.

Sweetpotato is a globally important food crop that plays a crucial role in food security in developing countries where it is often grown under marginal conditions. Sweetpotato yield is determined by the number of adventitious roots (ARs) that forms storage roots (SRs). Recent information indicates that sweetpotato root system architecture (RSA) is related to the competency of an AR to undergo SR formation (SRF). It has also been found that local nitrogen presence influenced sweetpotato RSA development which in turn influenced the uptake of mobile and non-mobile nutrients from the growth substrate. We considered this information in examining a LSQUOGeorgia JetRSQUO root transcriptome dataset to search for genes that are related to SRF, on one hand, and are responsive to nutrient availability, on the other. Using this approach, we found that putative nitrate (NO3-) and ammonium transporters were down-regulated in initiating SRs, while a putative potassium transporter was up-regulated. In addition, we found that a homologue of the Arabidopsis ANR1 gene, a component of the signalling pathway that links external NO3- to RSA development, shows up-regulated expression in initiating SRs. The same gene sequence exhibits homology to IbMADS1, shown previously to act as positive regulators of cell proliferation in root vascular tissue leading to SRF. Taken together, the evidence suggests that RSA provides an important link between environmental signals (nutrient availability) and gene networks previously associated with SRF in sweetpotatoes. This information can be useful for efficiently identifying gene-based markers in breeding programs, especially for low-input environments.

Introduction Untargeted metabolomics is a powerful tool to detect hundreds of metabolites within a given tissue and to compare the metabolite composition of samples in a comprehensive manner. However, with regard to pollen research such comprehensive metabolomics approaches are yet not well developed. To enable isolation of pollen that is tightly enclosed within the anthers of the flower, such as immature pollen, the current pollen isolation protocols require the use of a watery solution. These protocols raise a number of concerns for their suitability in metabolomics analyses, in view of possible metabolic activities in the pollen and contamination with anther metabolites. Objectives We assessed the effect of different sample preparation procedures currently used for pollen isolation for their suitability to perform metabolomics of tomato pollen. Methods Pollen were isolated using different methods and the metabolic profiles were analysed by liquid chromatography–mass spectrometry (LC–MS). Results Our results demonstrated that pollen isolation in a watery solution led to (i) rehydration of the pollen grains, inducing marked metabolic changes in flavonoids, phenylpropanoids and amino acids and thus resulting in a metabolite profile that did not reflect the one of mature dry pollen, (ii) hydrolysis of sucrose into glucose and fructose during subsequent metabolite extraction, unless the isolated and rehydrated pollen were lyophilized prior to extraction, and (iii) contamination with anther-specific metabolites, such as alkaloids, thus compromising the metabolic purity of the pollen fraction. Conclusion We conclude that the current practices used to isolate pollen are suboptimal for metabolomics analyses and provide recommendations on how to improve the pollen isolation protocol, in order to obtain the most reliable metabolic profile from pollen tissue. Electronic supplementary material The online version of this article (10.1007/s11306-018-1471-4) contains supplementary material, which is available to authorized users.

Recently, we have developed a quantitative shotgun proteomics strategy called mass accuracy precursor alignment (MAPA). The MAPA algorithm uses high mass accuracy to bin mass-to-charge (m/z) ratios of precursor ions from LC-MS analyses, determines their intensities, and extracts a quantitative sample versus m/z ratio data alignment matrix from a multitude of samples. Here, we introduce a novel feature of this algorithm that allows the extraction and alignment of proteotypic peptide precursor ions or any other target peptide from complex shotgun proteomics data for accurate quantification of unique proteins. This strategy circumvents the problem of confusing the quantification of proteins due to indistinguishable protein isoforms by a typical shotgun proteomics approach. We applied this strategy to a comparison of control and heat-treated tomato pollen grains at two developmental stages, post-meiotic and mature. Pollen is a temperature-sensitive tissue involved in the reproductive cycle of plants and plays a major role in fruit setting and yield. By LC-MS-based shotgun proteomics, we identified more than 2000 proteins in total for all different tissues. By applying the targeted MAPA data-processing strategy, 51 unique proteins were identified as heat-treatment-responsive protein candidates. The potential function of the identified candidates in a specific developmental stage is discussed.

UNLABELLED • PREMISE OF THE STUDY Yield in sweetpotato is determined by the number of storage roots produced per plant. Storage roots develop from adventitious roots (ARs) present in stem cuttings that serve as propagation material. Data on the origin of sweetpotato ARs and the effect of nodal position on AR establishment and further development are limited.• METHODS We anatomically described root primordium initiation using stem sections and measured number of root primordia formed at different nodal positions using light microscopy and correlated nodal positions with AR number and length 14 d after planting (DAP).• KEY RESULTS Primordia for ARs initiate at the junction of the stem pith ray and the cambium, on both sides of the leaf gap, and they are well developed before emerging from the stem. The number of ARs that develop from isolated stem nodes 14 DAP corresponded to the number of AR primordia detected inside the stem. The total length of established roots at nodes 9-13 from the apex is about 2-fold longer than at nodes 5-8.• CONCLUSIONS Nodal position (age) has a significant effect on the developmental status and number of root primordia inside the stem, determining the number and length of ARs that have developed by 14 DAP. Adventitious roots originating from nodes 9-13 possess similar AR systems and develop better than those originating from younger nodes 3-8. The mechanism regulating AR initiation in nodes is discussed. This system can serve for studying the effect of environmental conditions on AR initiation, development, and capacity to form storage roots.

Streptococcus agalactiae (Group B Streptococcus or GBS) is a frequent cause of serious disease in newborns and adults. Epidemiological evidence indicates a strong association between GBS strains belonging to the hypervirulent CC17 clonal complex and the occurrence of meningitis in neonates. We investigate here the role of PbsP, a cell wall plasminogen binding protein, in colonization of the central nervous system by CC17 GBS. Deletion of pbsP selectively impaired the ability of the CC17 strain BM110 to colonize the mouse brain after intravenous challenge, despite its unchanged capacity to persist at high levels in the blood and to invade the kidneys. Moreover, immunization with a recombinant form of PbsP considerably reduced brain infection and lethality. In vitro, pbsP deletion markedly decreased plasmin-dependent transmigration of BM110 through brain microvascular endothelial cells. Although PbsP was modestly expressed in bacteria grown under standard laboratory conditions, pbsP expression was markedly upregulated during in vivo infection or upon contact with cultured brain endothelial cells. Collectively, our studies indicate that PbsP is a highly conserved Plg binding adhesin, which is functionally important for invasion of the central nervous system by the hypervirulent CC17 GBS. Moreover, this antigen is a promising candidate for inclusion in a universal GBS vaccine.

It is becoming increasingly evident that optimization of root architecture for resource capture is vital for enabling the next green revolution. Although cereals provide half of the calories consumed by humans, root and tuber crops are the second major source of carbohydrates globally. Yet, knowledge of root architecture in root and tuber species is limited. In this opinion article, we highlight what is known about the root system in root and tuber crops, and mark new research directions towards a better understanding of the relation between root architecture and yield. We believe that unraveling the role of root architecture in root and tuber crop productivity will improve global food security, especially in regions with marginal soil fertility and low-input agricultural systems.

Greenhouse and field culture systems were used to study the effect of drought conditions on the storage root (SR) formation in ‘Beauregard’ sweetpotato (Ipomoea batatas). In the greenhouse culture system, drought was simulated by withholding water for 5 and 10 days after transplanting (DAT) cuttings in dry sand. Control plants received water at planting and every 3 days thereafter. In the field studies, natural drought conditions and selective irrigation were used to impose water deprivation during the critical SR formation period. Greenhouse drought for 5 and 10 DAT reduced the number of SRs by 42% and 66%, respectively, compared with the controls. Field drought resulted in a 49% reduction in U.S. #1 SR yield compared with the irrigated condition. Quantitative real-time polymerase chain reaction (PCR) analysis showed differential expression of a set of sweetpotato transcription factors and protein kinases among greenhouse-grown plants subjected to well-watered conditions and water deficit during 5 DAT. A significant enhancement of expression was observed for known drought stress-associated genes such as an abscisic acid-responsive elements-binding factor, dehydration-responsive element-binding factor, and homeo-domain-zip proteins. Members of calcium-binding proteins showed differential expression under drought stress. For the first time it is reported that knotted1-like homeobox and BEL1-like genes showed altered expression in response to drought stress under a greenhouse condition. In summary, the results suggest that water deprivation during the SR formation period influences root development and expression patterns of stress-responsive genes and those previously found associated with SR formation in sweetpotato.

A partir de la documentation disponible pour la province romaine d’Egypte (30 av. J.‑C. – debut du ive siecle ap. J.‑C.), l’article propose de revisiter la notion de « mort violente » bien presente dans l’Antiquite romaine et de comprendre quelles formes de violence entrent en jeu. L’etude se limite aux morts individuelles. Elle exclut les morts qui revetent une dimension collective et qui resultent d’un massacre volontaire d’une partie de la population. Une premiere partie est consacree aux indices permettant d’identifier une mort violente. Certaines causes de deces sont explicitement mentionnees dans les sources, tandis que, parfois, seuls des termes specifiques denotent implicitement une mort violente. L’analyse scientifique des corps contribue egalement a mettre en evidence des coups mortels. Une deuxieme partie aborde la signification de ces morts violentes. En effet, ces dernieres sont, dans une certaine mesure, un indicateur de la violence ambiante dans la province romaine d’Egypte. L’attention que leur porte le pouvoir en place temoigne de la volonte de Rome de gerer la mort et d’encadrer la population. Enfin, le rapport aux defunts decedes de mort violente traduit un imaginaire collectif particulier.

This study aimed to investigate the effect of 1-methylcyclopropene (1-MCP) on adventitious rooting in two sweetpotato cultivars. Experiments with ‘Beauregard’ and ‘Evangeline’ sweetpotato cuttings revealed differential adventitious root (AR) emergence responses to 1-MCP application. ‘Beauregard’ AR count and length decreased with 1-MCP application in two of four experiments. In contrast, 1-MCP did not influence ‘Evangeline’ root count. However, ‘Evangeline’ root length decreased in three of four experiments. Trypan blue staining of ‘Beauregard’ nodal tissue with delayed AR primordia emergence showed localized dead tissue in the general area where ARs emerge. The degree of staining appeared to correspond with the stage of AR emergence with the staining becoming more intense around the time an AR primordium eventually emerged through a crack in the epidermis. This response agrees with reported results of ethylene-mediated AR emergence in other plant species. These results also appear to suggest that ‘Beauregard’ and ‘Evangeline’ cuttings differ in ethylene sensitivity. This represents the first evidence of genotype-specific ethylene involvement in adventitious rooting of sweetpotato cuttings.

This study characterized lateral root (LR) development attributes during the onset of storage root (SR) initiation stage in ‘Beauregard’ sweetpotato. SR initiation has been defined as the appearance of cambia around the protoxylem and secondary xylem elements. Our results showed that 20-day-old adventitious roots (ARs) classified as SRs had 53% and 85% greater mean LR count than pencil roots (PRs) and lignified roots (LGs), respectively. SRs had 53% and 78% greater mean LR density relative to PRs and LGs, respectively. SRs had 66% and 130% greater mean total LR length than PRs and LGs, respectively. SRs had lower mean main root (MR)/LR length ratio compared with PRs (–38%) and LGs (–60%). SRs had 70% and 134% greater mean surface area than PRs and LGs, respectively. SRs had lower mean MR/LR surface area ratio compared with PRs (–42%) and LGs (–62%). The plot of the first and second principal components revealed the presence of a gradient between extreme LG and SR clusters, suggesting a developmental transition between LGs and SRs with PRs representing an intermediate developmental stage. Although AR architecture is not the sole determinant of SR formation, our data help provide a basis for integrating AR architecture attributes with other factors that are known to influence SR initiation. Growth substrate moisture variability influenced LR development during the critical SR initiation period. Relative to the control treatments, water deprivation 10 to 20 days after transplanting (DAT) reduced mean LR count, length, and surface area by 49%, 103%, and 94%, respectively. Saturated conditions 10 to 20 DAT reduced mean LR count, length, and surface area by 75%, 81%, and 77%, respectively. These results represent the first evidence for the association between anatomical cues of SR initiation and root architecture and provide corroborating data that soil moisture variability 10 to 20 DAT directly influences SR yield potential through AR architecture modifications that are associated with diminished SR formation. This information can be used to further optimize SR yield by identifying agroclimatic and management variables that are associated with desirable LR development during the critical SR initiation stage.

The formation of mature and fertile pollen grains, taking place inside the anther, depends on supply of assimilates, in the form of sucrose, provided mainly by the leaves. Data is limited, however, with respect to the understanding of sucrose metabolism in microspores and the supporting tissues. The aims of the present work were to 1) follow the changes in total and relative concentrations of sucrose, glucose, fructose and starch in the stamen parts and microspores up until anthesis, 2) follow the activities of sucrose-metabolism-related enzymes, in the anther walls fraction and microspores of the crop plant tomato. Sucrose was found to be partially cleaved in the filament, decreasing by more than twofold in the anther wall layers and the locular fluid, and to accumulate in the mature pollen grains, constituting 80% of total soluble sugars. Thus, sucrose was both the starting sugar, supporting microspore development, and the main carbohydrate accumulated at the end of the pollen-development program. The major invertase found to be active in both the anther wall layers and in maturing microspores was cell-wall-bound invertase. High fructokinase 2 and sucrose phosphate synthase activities during pollen maturation coincided with sucrose accumulation. The potential importance of sucrose accumulation during pollen dehydration phase and germination is discussed.

Because oxygen cannot be fully eliminated from organic solar cells, the occurrence of oxidative photo-degradation of the device in operating conditions has to be considered. Polyphenylene-vinylene-based photovoltaic devices have a short lifetime that currently limits their applications. In this article, we focus on various transient species that are potentially involved in the initiation step of the photo-oxidation of poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] (MDMO-PPV). The role of the transient species was investigated by a combination of quenching and sensitization experiments. Complementary information was obtained by transient absorption spectroscopy. Results evidenced the fact that 1O2 was not the principal reactive intermediate involved in the photo-oxidation of MDMO-PPV. This result was in contradiction with previous reports. It was shown that the MDMO-PPV•+ radical cation was generated after excitation. The presence of oxygen and the photo-aging favored the formation of the radical cation, suggesting that oxygen and photoproducts act as electron acceptors. The charged radicals formed are likely to evolve and give radicals that initiate the oxidation of the polymer by abstraction of the labile hydrogen in α position of the ether function and by addition on the double bonds. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6044–6052, 2009

Above-optimal temperatures reduce yield in tomato largely because of the high heat stress (HS) sensitivity of the developing pollen grains. The high temperature response, especially at this most HS-sensitive stage of the plant, is poorly understood. To obtain an overview of molecular mechanisms underlying the HS response (HSR) of microspores, a detailed transcriptomic analysis of heat-stressed maturing tomato microspores was carried out using a combination of Affymetrix Tomato Genome Array and cDNA-amplified fragment length polymorphism (AFLP) techniques. The results were corroborated by reverse transcription-PCR (RT-PCR) and immunoblot analyses. The data obtained reveal the involvement of specific members of the small heat shock protein (HSP) gene family, HSP70 and HSP90, in addition to the HS transcription factors A2 (HSFA2) and HSFA3, as well as factors other than the classical HS-responsive genes. The results also indicate HS regulation of reactive oxygen species (ROS) scavengers, sugars, plant hormones, and regulatory genes that were previously implicated in other types of stress. The use of cDNA-AFLP enabled the detection of genes representing pollen-specific functions that are missing from the tomato Affymetrix chip, such as those involved in vesicle-mediated transport and a pollen-specific, calcium-dependent protein kinase (CDPK2). For several genes, including LeHSFA2, LeHSP17.4-CII, as well as homologues of LeHSP90 and AtVAMP725, higher basal expression levels were detected in microspores of cv. Hazera 3042 (a heat-tolerant cultivar) compared with microspores of cv. Hazera 3017 (a heat-sensitive cultivar), marking these genes as candidates for taking part in microspore thermotolerance. This work provides a comprehensive analysis of the molecular events underlying the HSR of maturing microspores of a crop plant, tomato.

A thermal time-based approach using growing degree days was used to describe the onset of morpho-anatomical features associated with storage root developmental stages in the sweetpotato cultivar ‘Beauregard.’ Initially, we calculated accumulated growing degree days corresponding to adventitious root initiation, the onset of storage root formation (appearance of anomalous cambium), and appearance of visible storage roots with localized thickening and pigmentation in sweetpotatoes grown under greenhouse conditions. Subsequently, we performed field calibration of this approach to verify the timing of these storage root developmental stages under natural growing conditions. Under field conditions, transplants required relatively fewer calendar days to achieve the thermal time corresponding to each developmental stage in comparison to greenhouse-grown plants. Further calibration of this approach for ‘Beauregard’ and other sweetpotato varieties grown in diverse environments will help enhance our understanding of the effects of management and agroclimatic variables on sweetpotato yield determination. This study demonstrates the advantage of using thermal time vs. calendar days in estimating storage root development in sweetpotatoes.

Additional index words. storage root development, storage root anatomy, Ipomoea batatas Abstract. Adventitious roots of 'Beauregard' and 'Georgia Jet' sweetpotato were observed and anatomically characterized over a period of 60 days of storage root development. The majority of 'Beauregard' and 'Georgia Jet' adventitious roots sampled at 5 to 7 days after transplanting (DAT) possessed anatomical features (five or more protoxylem elements) associated with storage root development. The majority of 'Beauregard'(86%)and'GeorgiaJet'(89%)storagerootssampledat60to65DATwere traced directly to adventitious roots extant at 5 to 7 DAT. The two varieties, however, differed in the timing in which regular and anomalous cambia were formed. Regular vascular cambium development, i.e., initiation and completion, was observed in both varieties at 19 to 21 DAT. Formation of complete regular vascular cambium was negligible for 'Beauregard' (4%) in comparison with 'Georgia Jet' (32%) at 26 to 28 DAT. However, anomalous cambia development adjacent to xylem elements was greater in 'Beauregard' (30%) in comparison with 'Georgia Jet' (13%). Nearly 40% to 50% of samples in both varieties showed extensive lignification in the stele region. At 32 to 35 DAT, 62% to 70% of the adventitious roots for both varieties had either been initiated (developed anomalous cambium) or were lignified. The remaining adventitious roots showed intermediate stages of vascular cambium development. The adventitious root count increased up to 19 to 21 DAT and then remained constant up to 32 to 35 DAT. These accumulatedresults suggestthatthe initialstages ofadventitiousrootdevelopment are critical in determining storage root set in sweetpotato.

International audience; The stereo-electronic control over bisadditions of conjugated polymers to fullerene (C60) is explored in the formation of alternating copolymers. The chemistry, resulting configuration, and properties of poly(3-hexylthiophene)- alt-C60 copolymers prepared by either classic pyrrolidine ring formation or an atom transfer radical addition are compared. Both routes result in controlled additions of polymers to C60. Extensive macromolecular modeling through PM6 methods indicate that there is no conjugation between P3HT and C60 in the systems studied. This along with 2D-NMR, AFM, and photovoltaic characterizations of the materials indicate the importance of the structure of the modified C60 and the nature of the linking group between C60 and P3HT segments in determining the morphology of the copolymers in the solid state. © 2009 Wiley Periodicals, Inc.

Exposure of MDMO-PPV and MDMO-PPV:PCBM to UV-visible light in deoxygenised atmosphere results in a slow evolution of the chemical structure of both components. A photodegradation mechanism of MDMO-PPV is proposed. Concerning MDMO-PPV:PCBM blends, the results indicated that the photodegradation of MDMO-PPV was significantly slowed down in the blend. Extrapolation of data obtained in the condition of artificially accelerated ageing suggests that, if well protected of oxygen (encapsulation), this active layer is photochemically stable for several years in real conditions of ageing. Moreover, the efficiently quenched fluorescence evidenced is promising concerning the charge separation all along the lifetime of the system.

International audience; This paper is devoted to the study of the photo- and thermal-ageing of MDMO-poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylene vinylene (PPV) blended with methano-fullerene[6,6]-phenyl C61-butyric acid methyl ester ([60] PCBM), a commonly used active layer of organic solar cells. Thin films of MDMO-PPV, PCBM and MDMO-PPV:PCBM were submitted to photo- and thermal ageing in presence or in absence of oxygen. The modifications of the chemical structure of the materials were analysed by UV-visible and IR spectroscopies. Studying the degradation of pristine materials (MDMO-PPV and PCBM) permit the identification of the markers for characterizing the degradation of each component of the active layer. The degradation of MDMO-PPV was shown to involve a radicalar oxidation implying at first the ethers functions and secondly the double bonds; the photo-oxidation of PCBM was shown to involve the oxidation of its C60 moiety. Photo-oxidation of MDMO-PPV:PCBM blends involved the degradation of both components and the presence of PCBM was observed to largely reduce the rate of degradation of MDMO-PPV in comparison with pristine MDMO-PPV. On a kinetic point of view, the same conclusion was obtained for thermo-oxidation and photolysis (irradiation in absence of oxygen). Our experimental results suggest that the decrease of the rate of degradation of MDMO-PPV in blended films during the three kind of ageing (hυ, T, O2) is mainly related to the radical scavenging properties of the PCBM.

Pollen thermotolerance. Global warming is predicted to increase the frequency and severity of extreme weather phenomena such as heat waves thereby posing a major threat for crop productivity and food security. The yield in case of most crop species is dependent on the success of reproductive development. Pollen development has been shown to be highly sensitive to elevated temperatures while the development of the female gametophyte as well as sporophytic tissues might also be disturbed under mild or severe heat stress conditions. Therefore, assessing pollen thermotolerance is currently of high interest for geneticists, plant biologists and breeders. A key aspect in pollen thermotolerance studies is the selection of the appropriate heat stress regime, the developmental stage that the stress is applied to, as well as the method of application. Literature search reveals a rather high variability in heat stress treatments mainly due to the lack of standardized protocols for different plant species. In this review, we summarize and discuss experimental approaches that have been used in various crops, with special focus on tomato, rice and wheat, as the best studied crops regarding pollen thermotolerance. The overview of stress treatments and the major outcomes of each study aim to provide guidelines for similar research in other crops.

We reviewed the status of the use of the prophylactic long-acting granulocyte colony-stimulating factors (G-CSFs) pegfilgrastim and lipegfilgrastim in gynecologic malignancies. Long-acting G-CSFs should not be used in weekly regimens. Filgrastim is not indicated in patients with febrile and/or severe neutropenia after administration of long-acting G-CSF in the same cycle. One study has shown a moderate effect on febrile neutropenia of ciprofloxacin when co-administered with pegfilgrastim. There is broad evidence from meta-analyses that pegfilgrastim effectively reduces severe neutropenia. In parallel, its adverse effects have been studied extensively. All-cause mortality was significantly reduced by pegfilgrastim. The glycopegylated long-acting G-CSF, lipegfilgrastim has demonstrated antineutropenic efficacy similar to that of pegfilgrastimin in one breast cancer study. In another pivitol non-small cell lung cancer study, impaired survival was observed in the lipegfilgrastim group during the first 30 days of study. The European Medicines Agency claimed more profound safety data to be provided for lipegfilgrastim by 2017.

Sequencing costs are falling, but the cost of data analysis remains high, often because unforeseen problems arise, such as insufficient depth of sequencing or batch effects. Experimenting with data analysis methods during the planning phase of an experiment can reveal unanticipated problems and build valuable bioinformatics expertise in the organism or process being studied. This protocol describes using R Markdown and RStudio, user-friendly tools for statistical analysis and reproducible research in bioinformatics, to analyze and document the analysis of an example RNA-Seq data set from tomato pollen undergoing chronic heat stress. Also, we show how to use Integrated Genome Browser to visualize read coverage graphs for differentially expressed genes. Applying the protocol described here and using the provided data sets represent a useful first step toward building RNA-Seq data analysis expertise in a research group.

Biotic and abiotic variables that influence sweetpotato root architecture development.

Hybrid concepts based on a nanoscale combination of organic and inorganic semiconductors are a promising way to enhance the cost efficiency of solar cells through a better use of the solar spectrum, a higher aspect ratio of the interface, and the good processability of polymers. A new type of solar cells has been investigated. It is based on a heterojunction between regio-regular poly(3-hexylthiophene) as an organic electron donor and silicon as an inorganic electron acceptor. In a first step towards nano-structured devices, cells made of flat thin films of these materials have been studied as a model case of the heterojunction. The materials were characterized through ellipsometry and absorption spectroscopy. The devices were studied by means of their spectral response and their I - V characteristics. By combining these results, the contribution of each layer and the mechanisms of photocurrent generation are explained. The best cells to-date show a power conversion efficiency of 1.6% under AM 1.5 illumination, with a V oc of 0.704 V and a J sc of 4.22 mA/cm 2 .

CdSe nanocrystals were modified with small ligand molecules in order to render them compatible with a conducting polymer matrix. Modified NCs were characterized by NMR, optical spectroscopy, electrochemistry. Hybrid materials based on such modified nanocrystals and a conducting polymer (MDMO-PPV, P3HT or P3OT) were prepared, characterized, and tested in photovoltaic devices. Modified NCs quench the polymer PL in solutions as well as in films. Photovoltaic devices display modest power conversion efficiencies mainly due to phase segregation.

Organic materials used in organic light emitting diodes (OLED) and organic solar cells are easily degraded under atmospheric conditions. Indeed, these devices require encapsulation with a barrier material which exhibits extremely low permeation rates for water vapour and oxygen. In order to determine these low permeation rates, the degradation of a metallic calcium layer encapsulated with the barrier material is usually monitored. However, the individual contributions of oxygen and water vapour to this degradation cannot be clearly distinguished. In this study, the corrosion of metallic calcium was investigated using isotopic markers in connection with ion beam analysis. We have shown that calcium reacts only with water at room temperature.

Exposure to high temperatures (heat stress) causes reduced yield in tomatoes (Lycopersicon esculentum), mainly by affecting male gametophyte development. Two experiments were conducted where several tomato cultivars were grown under heat stress, in growth chambers (day/night temperatures of 31/25 °C) or in greenhouses (day/night temperatures of 32/26 °C), or under control (day/night temperatures of 28/22 °C) conditions. In heat-sensitive cultivars, heat stress caused a reduction in the number of pollen grains, impaired their viability and germinability, caused reduced fruit set and markedly reduced the numbers of seeds per fruit. In the heat-tolerant cultivars, however, the number and quality of pollen grains, the number of fruits and the number of seeds per fruit were less affected by high temperatures. In all the heat-sensitive cultivars, the heat-stress conditions caused a marked reduction in starch concentration in the developing pollen grains at 3 days before anthesis, and a parallel decrease in the total soluble sugar concentration in the mature pollen, whereas in the four heat-tolerant cultivars tested, starch accumulation at 3 days before anthesis and soluble sugar concentration at anthesis were not affected by heat stress. These results indicate that the carbohydrate content of developing and mature tomato pollen grains may be an important factor in determining pollen quality, and suggest that heat-tolerant cultivars have a mechanism for maintaining the appropriate carbohydrate content under heat stress.

We describe in this article the quick optimization of bulk heterojunction organic solar cells based on poly-3-hexylthiophene and [6,6]-phenyl C61 butyric acid methylester blend. Best cells are found to be based on 1:1 in weight ratio and yield 3.6% power conversion efficiency under air-mass 1.5, 100 mW/cm2 illumination. On the optimized cells, ageing measurements have been realized to collect the absolute values of photovoltaic parameters along the time. On this study, accelerated lifetime has been calculated using the Arrhenius model for a first-order kinetic of degradation. According to the model, we can predict a long lifetime keeping more than 80% of the initial short-circuit current density after 1000 h of working.

SummaryExposure to high temperatures causes reduced yields in tomato (Lycopersicon esculentum), mainly by affecting male gametophyte development. The effect of heat stress on pollen characteristics...

The fungal cell wall field, traditionally focused on polysaccharide composition and synthesis, retains a certain static architectural imagery of structural rigidity and integrity, with the wall offering protection from a harsh environment. This picture of the wall is increasingly changing to that of a bustling construction site, as research uncovers the organizational complexity of its assembly. With recent molecular and genomic studies on Saccharomyces cerevisiae, cell wall synthesis and biology appear increasingly to be dynamic and adaptable processes that are fully integrated with the underlying cytoskeletal and polarity machinery that drive cell cycle progression.

The opportunistic pathogen Aspergillus fumigatus is the most frequent cause of deadly airborne fungal infections in developed countries. In order to identify novel antifungal-drug targets, we investigated the genome of A. fumigatus for genes that are necessary for efficient fungal growth. An artificial A. fumigatus diploid strain with one copy of an engineered impala160 transposon from Fusarium oxysporum integrated into its genome was used to generate a library of diploid strains by random in vivo transposon mutagenesis. Among 2,386 heterozygous diploid strains screened by parasexual genetics, 1.2% had a copy of the transposable element integrated into a locus essential for A. fumigatus growth. Comparison of genomic sequences flanking impala160 in these mutants with that of the genome of A. fumigatus allowed the characterization of 20 previously uncharacterized A. fumigatus genes. Among these, homologues of genes essential for Saccharomyces cerevisiae growth have been identified, as well as genes that do not have homologues in other fungal species. These results confirm that heterologous transposition using the transposable element impala is a powerful tool for functional genomics in ascomycota, and they pave the way for defining the complete set of essential genes in A. fumigatus , the first step toward target-based development of new antifungal drugs.

We have evaluated the usefulness of parasexual genetics in the identification of genes essential for the growth of the human fungal pathogen Aspergillus fumigatus. First, essentiality of the A. fumigatus AfFKS1 gene, encoding the catalytic subunit of the β-(1,3)-glucan synthase complex, was assessed by inactivating one allele of AfFKS1 in a diploid strain of A. fumigatus obtained using adequate selectable markers in spore color and nitrate utilization pathways and by performing haploidization under conditions that select for the occurrence of the disrupted allele. Haploid progeny could not be obtained, demonstrating that AfFKS1 and, hence, β-(1,3)-glucan synthesis are essential in A. fumigatus. Second, random heterozygous insertional mutants were generated by electroporation of diploid conidia with a heterologous plasmid. A total of 4.5% of the transformants failed to produce haploid progeny on selective medium. Genomic analysis of these heterozygous diploids led in particular to the identification of an essential A. fumigatus gene encoding an SMC-like protein resembling one in Schizosacccharomyces pombe involved in chromosome condensation and cohesion. However, significant plasmid and genomic DNA rearrangements were observed at many of the identified genomic loci where plasmid integration had occurred, thus suggesting that the use of electroporation to build libraries of A. fumigatus insertional mutants has relatively limited value and cannot be used in an exhaustive search of essential genes.

Background Calcium phosphate-adsorbed allergen extracts are used for subcutaneous immunotherapy to avoid the use of aluminium adjuvants. Objectives A double-blind, placebo-controlled study was performed in order to confirm the safety and assess the efficacy of a standardized five-grass-pollen extract adsorbed onto calcium phosphate for specific immunotherapy (IT). Methods Twenty-nine patients with seasonal rhinoconjunctivitis were randomized to receive either the active preparation (16 patients) or placebo (13 patients), in a 1-year study. During the increasing dose phase, an extract ranging from 0.1 IR per ml to 50 IR per ml was administered at a rate of one subcutaneous injection per week until a maintenance dose was reached. The patients were assessed by symptom diary and rescue medications during seasonal exposure and specific nasal and skin reactivity before and after IT. Immunological parameters (specific IgE and IgG 4 antibodies) were assessed before, during and after IT. Results The overall symptoms score (mean AUC) was not significantly different between the IT group and the placebo group during grass-pollen exposure (49.6 vs. 56, respectively). The total medication score (mean AUC) was significantly lower in the IT group than in the placebo group (11 vs. 41, P < 0.01, Mann-Whitney U-test). The cumulative symptom/medication score was significantly lower in the IT group than in the placebo group (64.5 VS. 102.3, P < 0.05, U-test). A significant increase in nasal reactivity threshold was observed after IT in the IT group (21. 4 IR/mL before IT vs. 63.4 IR/mL after IT, P < 0.01, Wilcoxon), whereas no significant changes were observed in the placebo group (31.0 IR/mL before IT vs. 37.7 IR/mL after IT). IT induced a significant reduction in grass pollen cutaneous reactivity in the actively treated group (P < 0.001). A significant increase in serum-specific IgG 4 antibody response was observed in the IT group (3.1% before IT VS. 10.1% after IT, P < 0.001). Nine patients in the IT group developed moderate immediate systemic reactions vs. two patients in the placebo group. Conclusion Specific immunotherapy with calcium phosphate-adsorbed standardized grass pollen extract was safe and effective for the treatment of patients with seasonal allergic rhinoconjunctivitis.

The cytoplasmic male-sterile (CMS) line CMS-pennellii (BC10P2 L. peruvianum×L. pennellii) and its complex hybrids with L. esculentum were studied. The established sterility was classified as the sporogenous type. As a result of the interaction of the genome of L. pennellii and the cytoplasm of L. peruvianum clear changes were established in the profiles of malic enzyme and esterase. Restriction fragment length polymorphism (RFLP) was detected between the mitochondrial (mt) genomes of CMS-pennellii and the cytoplasm donor, L. peruvianum, for two mtDNA probes: atpA and nad3. The established differences in the isozyme pattern and mt genomes are considered as useful markers to distinguish fertile and sterile plants. A breakthrough in the unilateral incompatibility of CMS-pennellii and the incorporation of the genome of L. esculentum on a CMS background is reported. The analysis of the complex hybrids assumes the interaction of two dominant genes – a maintainer gene from L. pennellii and a restorer gene from cultivated tomato. The hybrids produced with L. esculentum provide the basis for the development of a CMS system in cultivated tomato.

Silicon oxynitride thin films deposited by plasma enhanced chemical vapor deposition on various substrates have been characterized by infrared reflection absorption spectroscopy. Shifts of the LO Si–O vibrational band to lower wave numbers have been observed with increasing N content and also with the thickness of the films. We observe that the ratio of LO Si–O vibrational mode wave number to film thickness (υ/t) varies linearly with the ratio of refractive index to thickness (n/t). This linear relationship does not depend on the nature of substrates on which films are deposited (Al/Si, Si, Si/Al). Our results show that the composition of silicon oxynitride films could be determined directly by measuring the LO Si–O mode position.

In petunia, a mitochondrial (mt) locus, S-Pcf, has been found to be strongly associated with cytoplasmic male sterility (CMS). The S-Pcf locus consists of three open reading frames (ORF) that are co-transcribed. The first ORF, Pcf, contains parts of the atp9 and coxII genes and an unidentified reading frame, urf-s. The second and third ORFs contain NADH dehydrogenase subunit 3 (nad3) and ribosomal protein S12 (rps12) sequences, respectively. The nad3 and rps12 sequences included in the S-Pcf locus are identical to the corresponding sequences on the mt genome of fertile petunia. In both CMS and fertile petunia, only a single copy of nad3 and rps12 had been detected on the physical map of the main mt genome. The origin of the urf-s sequence and the molecular events leading to the formation of the chimeric S-Pcf locus are not known. This paper presents evidence indicating that two different mt sequences, related to urf-s and found in fertile petunia lines (orf-h and Rf-1), might have been involved in the molecular evolution of the S-Pcf locus. Southern analysis of mtDNA derived from both fertile and sterile petunia plants suggests that one of these urf-s related sequences (showing 100% homology to urf-s and termed orf-h) is located on a sublimon. An additional, low-homology urf-s related sequence (Rf-1) is shown to be located on the main mt genome 5' to the nad3 gene. It is, thus, suggested that the sequence of events leading to the generation of the S-Pcf locus might have involved introduction of the orf-h sequence, via homologous recombination, into the main mt genome 5' to nad3 at the region where the Rf-1 sequence is located.

The paper supports the view that ethylene plays a significant role in maintaining tomato pollen thermotolerance. Interfering with the ethylene signalling pathway or reducing ethylene levels and increased tomato pollen sensitivity to heat stress. On the other hand, increasing ethylene levels before heat-stress improved pollen quality., Background and aims Exposure to higher-than-optimal temperatures reduces crop yield and quality, mainly due to sensitivity of developing pollen grains. The mechanisms maintaining high pollen quality under heat-stress conditions are poorly understood. Our recently published data indicate high heat-stress-induced expression of ethylene-responsive genes in tomato pollen, indicating ethylene involvement in the pollen heat-stress response. Here we elucidated ethylene's involvement in pollen heat-stress response and thermotolerance by assessing the effects of interfering with the ethylene signalling pathway and altering ethylene levels on tomato pollen functioning under heat stress. Methodology Plants of the ethylene-insensitive mutant Never ripe (Nr)—defective in an ethylene response sensor (ERS)-like ethylene receptor—and the corresponding wild type were exposed to control or heat-stress growing conditions, and pollen quality was determined. Starch and carbohydrates were measured in isolated pollen grains from these plants. The effect of pretreating cv. Micro-Tom tomato plants, prior to heat-stress exposure, with an ethylene releaser or inhibitor of ethylene biosynthesis on pollen quality was assessed. Principal results Never ripe pollen grains exhibited higher heat-stress sensitivity, manifested by a significant reduction in the total number of pollen grains, reduction in the number of viable pollen and elevation of the number of non-viable pollen, compared with wild-type plants. Mature Nr pollen grains accumulated only 40 % of the sucrose level accumulated by the wild type. Pretreatment of tomato plants with an ethylene releaser increased pollen quality under heat stress, with an over 5-fold increase in the number of germinating pollen grains per flower. Pretreatment with an ethylene biosynthesis inhibitor reduced the number of germinating pollen grains following heat-stress exposure over 5-fold compared with non-treated controls. Conclusions Ethylene plays a significant role in tomato pollen thermotolerance. Interfering with the ethylene signalling pathway or reducing ethylene levels increased tomato pollen sensitivity to heat stress, whereas increasing ethylene levels prior to heat-stress exposure increased pollen quality.

Over-expression is a valid functional genomics approach to characterise genes of unknown function on a genome-wide scale. Strains are engineered to over-express a specific gene and the resulting gain-of-function phenotype assessed. Here, we describe the strategy we are adopting to synthesise a Candida albicans ORFeome collection and the options available to create over-expressing strains from this collection.

Over-expression is a valid functional genomics approach to characterise genes of unknown function on a genome-wide scale. Strains are engineered to over-express a specific gene and the resulting gain-of-function phenotype assessed. Here, we describe the strategy we are adopting to synthesise a Candida albicans ORFeome collection and the options available to create over-expressing strains from this collection.