Reactive electrophile species.

The interest in reactive electrophile species (RES) stems largely from the fact that they can have powerful biological activities. RES stimulate the expression of cell survival genes as well many other genes commonly upregulated in environmental stress and pathogenesis. RES levels must be carefully controlled in healthy cells but their formation and destruction during stress is of great interest. Unlike many 'classical' signals and hormones, RES can potentially affect gene expression at all levels by chemically reacting with nucleic acids, proteins and small molecules as well as by indirectly lowering pools of cellular reductants. Recent works involving genetic approaches have begun to provide compelling evidence that, although excess RES production can lead to cell damage, lower levels of RES may modulate the expression of cell survival genes and may actually contribute to survival during severe stress.

Reduced peroxisomal citrate synthase activity increases substrate availability for polyhydroxyalkanoate biosynthesis in plant peroxisomes.

Polyhydroxyalkanoates (PHAs) are bacterial carbon storage polymers used as renewable, biodegradable plastics. PHA production in plants may be a way to reduce industrial PHA production costs. We recently demonstrated a promising level of peroxisomal PHA production in the high biomass crop species sugarcane. However, further production strategies are needed to boost PHA accumulation closer to commercial targets. Through exogenous fatty acid feeding of Arabidopsis thaliana plants that contain peroxisome-targeted PhaA, PhaB and PhaC enzymes from Cupriavidus necator, we show here that the availability of substrates derived from the β-oxidation cycle limits peroxisomal polyhydroxybutyrate (PHB) biosynthesis. Knockdown of peroxisomal citrate synthase activity using artificial microRNA increased PHB production levels approximately threefold. This work demonstrates that reduction of peroxisomal citrate synthase activity may be a valid metabolic engineering strategy for increasing PHA production in other plant species.

Unraveling the complex network of cuticular structure and function.

A hydrophobic cuticle is deposited at the outermost extracellular matrix of the epidermis in primary tissues of terrestrial plants. Besides forming a protective shield against the environment, the cuticle is potentially involved in several developmental processes during plant growth. A high degree of variation in cuticle composition and structure exists between different plant species and tissues. Lots of progress has been made recently in understanding the different steps of biosynthesis, transport, and deposition of cuticular components. However, the molecular mechanisms that underlie cuticular function remain largely elusive.

Validación chilena del cuestionario de evaluación de apego en el adulto CAMIR

El objetivo de esta investigación fue examinar la confiabilidad y validez del instrumento de evaluación de apego en el adulto, "Cartes: Modèles Individuels de Relation (CAMIR), en la realidad sociocultural chilena. Este instrumento, basado en la teoría del apego, es un cuestionario de auto-reporte que evalúa los modelos operativos internos en adultos y otras escalas relacionadas al apego. Los participantes fueron 578 sujetos, 204 hombres y 374 mujeres, con edades entre 14 y 80 años. Los sujetos completaron el CAMIR y medidas de vínculo y sintomatología actual, a través del Parental Bonding Instrument (PBI) and Outcome Questionnaire OQ-45.2. A través del análisis estadístico de los resultados se evaluaron las características psicométricas del test y de analiz ó la posibilidad de generar normas locales para la prueba. Los resultados confirmaron que el CAMIR es un instrumento confiable y válido en la evaluación de los modelos internos de relación en adultos. This study was designed to estimate the validity and reliability of the "Cartes: Modèles Individuels de Relation (CAMIR), in Chile. This inventory, based on attachment's theory, it's a auto-questionnaire evaluates the working models in adults and other scales relating to attachment. Participants were 578 individuals, 204 males and 374 females, 14 a 80 years old. Individuals completed the CAMIR and measures of bond and actual symptoms, with the Parental Bonding Instrument (PBI) and Outcome Questionnaire OQ-45.2. The general norms were obtained according to a statistical analysis of the results and to an evaluation of the psychometric characteristics of the test. The results confirmed that the psychometric characteristics of the CAMIR make it a reliable and valid tool to assess working models in adults.

Membrane and walls: who is master, who is servant?

Specialised plant cell types often locally modify their cell walls as part of a developmental program, as do cells that are challenged by particular environmental conditions. Modifications can include deposition of secondary cellulose, callose, cutin, suberin or lignin. Although the biosyntheses of cell wall components are more and more understood, little is known about the mechanisms that control localised deposition of wall materials. During metaxylem vessel differentiation, site-specific cell wall deposition is locally prevented by the microtubule depolymerising protein MIDD1, which disassembles the cytoskeleton and precludes the cellulose synthase complex from depositing cellulose. As a result, metaxylem vessel secondary cell wall appears pitted. How MIDD1 is tethered at the plasma membrane and how other cell wall polymers are locally deposited remain elusive. Casparian strips in the root endodermis represent a further example of local cell wall deposition. The recent discovery of the Casparian Strip membrane domain Proteins (CASPs), which are located at the plasma membrane and are important for the site-specific deposition of lignin during Casparian strip development, establishes the root endodermis as an attractive model system to study the mechanisms of localised cell wall modifications. How secondary modifications are modulated and monitored during development or in response to environmental changes is another question that still misses a complete picture.

Let there be light in the nucleus!

Ambient light conditions trigger both developmental transitions, such as the induction of flowering, and a suite of adaptive responses, exemplified by the shade-avoidance syndrome. These responses are initiated by three families of photoreceptors that are conserved in all higher plants: the phototropins, cryptochromes and phytochromes (phyA--phyE, cry1--cry3, phot1 and phot2 in Arabidopsis). Molecular genetic studies performed mainly in Arabidopsis indicate that photon capture by these light sensors usually initiates rapid changes in the gene expression profile, leading to plant adaptation to their environment. Interestingly, numerous transcription factors are early targets of light regulation, both at the transcriptional and post-transcriptional levels.

Plant defense against herbivory: progress in identifying synergism, redundancy, and antagonism between resistance traits.

Plants respond to herbivore attack through a complex and variable system of defense, involving different physical barriers, toxic chemicals, and recruitment of natural enemies. To fully understand the relative role of each type of defense, their synergisms, redundancies, or antagonisms between traits, a variety of methods of enquiry, commonly used in plant physiology and ecology, have been employed. By overexpressing or silencing genes of interest, it is possible to understand the specific role of a particular defensive molecule or mode of action. We argue, however, that these types of experiments alone are not enough to holistically understand the physiological as well as ecological role of plant defenses. We thus advocate for the use of a combination of methods, including genetic modification, quantitative genetics, and phylogenetically controlled comparative studies.

Cell polarity in plants: a PARspective on PINs.

Plants have acquired the ability for organized multicellular development independent from animals. Because of this, they represent an independent example in nature for the development of coordinated, complex cell polarity from the simple polarity found in unicellular eukaryotes. Plants display a striking array of polarized cell types, with different axes of polarity being defined in one cell. The most investigated and best understood aspect of plant polarity is the apical-basal polarity of the PIN family of auxin efflux facilitators, which are of crucial importance for the organization of the entire plant body. Striking differences exist between the PAR-polarity modules known in animals and the ways PINs polarize plant cells. Nonetheless, a common regulatory logic probably applies to all polarizing eukaryotic cells, which includes self-reinforcing, positive feedback loops, intricate interactions between membrane-attached proteins, lipid signatures, and the targeting of transmembrane proteins to the correct domains of the plasma membrane.

Spouse similarity in recollections of parenting received : a study in a nonclinical sample

Rapport de synthèse : L'article constituant le présent travail de thèse décrit une recherche portant sur des couples adultes recrutés dans la population générale, décrivant rétrospectivement les attitudes de leurs parents respectifs envers eux au cours de leur enfance. Le rôle joué par les attitudes d'attachement dans les relations adultes, et notamment les relations de couples, est bien démontré. De même, il est établi que les relations établies avec les parents dans l'enfance influencent le type d'attitude d'attachement qui prédominera à l'âge adulte. Dès lors, nous avons investigué l'existence, au sein de ces couples adultes, de souvenirs similaires quant aux attitudes prodiguées par les parents. Pour réaliser cette recherche, nous avons contacté tous les parents des enfants scolarisés en 2e/3e années et en 6e/7e années au sein des écoles de plusieurs communes de la région lausannoise, permettant de constituer un échantillon de 563 couples de parents. Au moyen d'autoquestionnaires, nous avons évalué pour chaque membre du couple : 1) sa description rétrospective des attitudes de ses deux parents envers lui pendant son enfance ; 2) le degré de sa symptomatologie psychiatrique actuelle ; et 3) son évaluation du degré d'ajustement dyadique actuel au sein du couple. La comparaison des scores des époux respectifs sur « l'échelle de lien parental » (PBI : Parental Bonding Instrument) a montré une ressemblance, au sein des couples, concernant la c chaleur et affection » (« Care ») témoignée au cours de l'enfance parle parent de même sexe que le sujet. Les analyses complémentaires effectuées semblent exclure que cette similarité soit due à des facteurs confondant comme l'âge, l'origine culturelle, le niveau socio-économique, ou le degré de symptomatologie psychiatrique. De même, cette similarité ne semble pas être attribuable à une convergence de vue grandissante des conjoints au cours de leur union. Par ailleurs, le degré d'ajustement dyadique s'est révélé être dépendant du degré cumulé de chaleur et d'affection tel que remémoré par chaque conjoint, et non du degré de similarité dans le couple pour ce qui concerne le souvenir de la chaleur et de l'affection reçues. Bien que basée sur des évaluations rétrospectives des attitudes parentales, et ne disposant pas d'une investigation psychiatrique standardisée incluant les critères diagnostiques, cette étude repose néanmoins sur un grand échantillon, recruté dans la population générale. Nos résultats ont notamment des implications concernant la santé des enfants. En effet, en raison de la similarité mise en évidence dans nos résultats, un enfant dont un des parents a reçu peu de chaleur et d'affection dans son enfance a plus de chances que son autre parent aie lui-même également reçu moins de chaleur et d'affection. De ce fait, d'une part l'ajustement dyadique du couple parental sera particulièrement bas, ce qui peut se répercuter sur les enfants du couple. D'autre part, comme les attitudes parentales se transmettent en partie de génération en génération, le même enfant risque d'être exposé, de la part de ses deux parents, à une attitude comportant peu de chaleur et d'affection, ce qui représente un risque de développement ultérieur des pathologies psychiatriques chez cet enfant.

Beta-oxidation in fatty acid degradation and beyond.

The degradation of fatty acids in plants occurs primarily in the peroxisomes through the beta-oxidation cycle. Enzymes that are involved in various aspects of beta-oxidation have been identified recently and shown to act biochemically on a diversity of fatty acids and derivatives. Analysis of several mutants has revealed essential roles for beta-oxidation in the breakdown of reserve triacylglycerols, seed development, seed germination and post-germinative growth before the establishment of photosynthesis. Beta-oxidation has also a considerable importance during the vegetative and reproductive growth phases, and plays a role in plant responses to stress, particularly in the synthesis of jasmonic acid.

Higher plants use LOV to perceive blue light.

Higher plants use several classes of blue light receptors to modulate a wide variety of physiological responses. Among them, both the phototropins and members of the Zeitlupe (ZTL) family use light oxygen voltage (LOV) photosensory domains. In Arabidopsis, these families comprise phot1, phot2 and ZTL, LOV Kelch Protein 2 (LKP2), and Flavin-binding Kelch F-box1 (FKF1). It has now been convincingly shown that blue-light-induced autophosphorylation of the phot1 kinase domain is an essential step in signal transduction. Recent experiments also shed light on the partially distinct photosensory specificities of phot1 and phot2. Phototropin signaling branches rapidly following photoreceptor activation to mediate distinct responses such as chloroplast movements or phototropism. Light activation of the LOV domain in ZTL family members modulates their capacity to interact with GIGANTEA (GI) and their ubiquitin E3 ligase activity. A complex between GI and FKF1 is required to trigger the degradation of a repressor of CO (CONSTANS) expression and thus modulates flowering time. In contrast, light-regulated complex formation between ZTL and GI appears to limit the capacity of ZTL to degrade its targets, which are part of the circadian oscillator.

Suberization-the second life of an endodermal cell.

The endodermis is the innermost cortical cell layer that surrounds the central vasculature and deposits an apoplastic diffusion barrier known as the Casparian strip. Although discovered 150 years ago, the underlying mechanisms responsible for formation of the Casparian strips have only recently been investigated. However, the fate of the endodermal cell goes further than formation of Casparian strips as they undergo a second level of differentiation, defined by deposition of suberin as a secondary cell wall. The presence and function of endodermal suberin in root barriers has remained enigmatic, as its role in barrier formation is not clear, especially in respect to the already existing Casparian strips. In this review, we present recent advances in the understanding of suberin synthesis, transport to the secondary cell wall, developmental features and functions. We focus on some of the major unknown questions revolving the function of endodermal suberin, which we now have the means to investigate. We further provide thoughts on how this knowledge might expand our current models on the developmental and physiological adaptation of root in response to the environment.

Secondary growth of the Arabidopsis hypocotyl-vascular development in dimensions.

The secondary thickening of plant organs in extant dicotyledons is a massive growth process that constitutes the major carbon sink in perennial, woody plants. Yet, our understanding of its molecular genetic control has been mostly obtained by its analysis in an herbaceous annual model, Arabidopsis. Recent years have seen increased interest in this somewhat under-researched topic, and various (non-)cell autonomous factors that guide the extent and vascular patterning of secondary growth have been identified. Concomitantly, a more detailed understanding of vascular differentiation processes has been obtained through analyses of primary growth, mostly in the root meristem. A future challenge will be the integration of these patterning and differentiation modules together with cambial activity into the 4-dimensional frame of secondary thickening.