De grafemische buffer : aspecten van een spellingstoornis

A spelling disorder that received much attention recently is the so-called graphemic buffer impairment. Caramazza et al. (1987) presented the first systematic case study of a patient with this disorder. Miceli & Capasso (2006) provide an extensive overview of the relevant literature. This article adds to the literature by describing a Dutch case, i.e. patient BM. We demonstrate how specific features of Dutch and Dutch orthography interact with the graphemic buffer impairment. In addition, we paid special attention to the influence of grapheme position on the patient’s spelling accuracy. For this we used, in contrast with most of the previous literature, the proportional accountability method described in Machtynger & Shallice (2009). We show that by using this method the underlying error distribution can be more optimally captured than with classical methods. The result of this analysis replicates two distributions that have been previously reported in the literature. Finally, attention will be paid to the role of phonology in the described disorder

De grafemische buffer : aspecten van een spellingstoornis

Ce riche volume de 373 pages rassemble les contributions pour un colloque qui fut organisé les 30 novembre et 1 décembre 2012 par le “Centro Studi Sigismondo Castromediano e Gino Rizzo” à Cavallino di Lecce. Le personnage historique de premier plan qui fait l’objet du volume est Sigismondo Castromediano (Cavallino 1811-1895), surnommé le « Bianco Duca », noble de la région des Pouilles, arrêté en 1848 pour activité patriotique au sein de la Giovine Italia, condamné à trente ans de bagne, puis..

Lateral root formation involving cell division in both pericycle, cortex and endodermis is a common and ancestral trait in seed plants

Studies on the model plant Arabidopsis have led to the common view that lateral roots are exclusively formed from pericycle cells and that the latter are unique in their ability to be reprogrammed into stem cells. By analysing lateral root formation in an evolutionary context, we show that lateral root primordium formation in which cortex, endodermis and pericycle are mitotically activated, is a common and ancestral trait in seed plants, whereas the exclusive involvement of pericycle evolved in the Brassicaceae. Furthermore, the endodermis can also be reprogrammed into stem cells in some species.</p

Use of the Fluorescent Timer DsRED-E5 as Reporter to Monitor Dynamics of Gene Activity in Plants

Fluorescent proteins, such as green fluorescent protein and red fluorescent protein (DsRED), have become frequently used reporters in plant biology. However, their potential to monitor dynamic gene regulation is limited by their high stability. The recently made DsRED-E5 variant overcame this problem. DsRED-E5 changes its emission spectrum over time from green to red in a concentration independent manner. Therefore, the green to red fluorescence ratio indicates the age of the protein and can be used as a fluorescent timer to monitor dynamics of gene expression. Here, we analyzed the potential of DsRED-E5 as reporter in plant cells. We showed that in cowpea (Vigna unguiculata) mesophyll protoplasts, DsRED-E5 changes its fluorescence in a way similar to animal cells. Moreover, the timing of this shift is suitable to study developmental processes in plants. To test whether DsRed-E5 can be used to monitor gene regulation in plant organs, we placed DsRED-E5 under the control of promoters that are either up- or down-regulated (MtACT4 and LeEXT1 promoters) or constitutively expressed (MtACT2 promoter) during root hair development in Medicago truncatula. Analysis of the fluorescence ratios clearly provided more accurate insight into the timing of promoter activity

Lateral root formation involving cell division in both pericycle, cortex and endodermis is a common and ancestral trait in seed plants

Studies on the model plant Arabidopsis have led to the common view that lateral roots are exclusively formed from pericycle cells and that the latter are unique in their ability to be reprogrammed into stem cells. By analysing lateral root formation in an evolutionary context, we show that lateral root primordium formation in which cortex, endodermis and pericycle are mitotically activated, is a common and ancestral trait in seed plants, whereas the exclusive involvement of pericycle evolved in the Brassicaceae. Furthermore, the endodermis can also be reprogrammed into stem cells in some species.</p

A genetically and functionally diverse group of non-diazotrophic Bradyrhizobium spp. colonizes the root endophytic compartment of Arabidopsis thaliana

Background: Diazotrophic Bradyrhizobium spp. are well known for their ability to trigger nodule formation on a variety of legume species. In nodules, Bradyrhizobium utilizes plant-derived carbohydrates in exchange for fixed nitrogen. The genes essential for the nodulation and nitrogen-fixation trait are clustered in a genomic region, which is known as the 'symbiotic island'. Recently, novel non-diazotrophic Bradyrhizobium spp. have been found to be highly abundant in soils, suggesting that these species can also have a 'free-living' life history. However, whether non-diazotrophic Bradyrhizobium spp. can live in association with plants remains elusive. Results: In this study, we show that Bradyrhizobium spp. are common root endophytes of non-legume plant species - including Arabidopsis thaliana (Arabidopsis) - grown in an ecological setting. From a single Arabidopsis root, four Bradyrhizobium sp. strains (designated MOS001 to MOS004) were isolated. Comparative genome analysis revealed that these strains were genetically and functionally highly diverse, but did not harbour the nodulation and the nitrogen fixation gene clusters. Comparative colonization experiments, with MOS strains and nitrogen-fixing symbiotic strains, revealed that all tested Bradyrhizobium spp. can colonize the root endophytic compartment of Arabidopsis. Conclusion: This study provides evidence that both diazotrophic and non-diazotrophic Bradyrhizobium spp. colonize the root endophytic compartment of a wide variety of plant species, including the model species Arabidopsis. This demonstrates that plant roots form a major ecological niche for Bradyrhizobium spp., which might be ancestral to the evolution of the nodulation and nitrogen-fixation trait in this genus

RNA interference in Agrobacterium rhizogenes-transformed roots of Arabidopsis and Medicago truncatula

RNA interference (RNAi) is a powerful reverse genetic tool to study gene function. The data presented here show that Agrobacterium rhizogenes-mediated RNAi is a fast and effective tool to study genes involved in root biology. The Arabidopsis gene KOJAK, involved in root hair development, was ef®ciently knocked down. A. rhizogenes-mediated root transformation is a fast method to generate adventitious, genetically transformed roots. In order to select for co-transformed roots a binary vector was developed that enables selection based on DsRED1 expression, with the additional bene®t that chimaeric roots can be discriminated. The identi®cation of chimaeric roots provided the opportunity to examine the extent of systemic spread of the silencing signal in the composite plants of both Arabidopsis and Medicago truncatula. It is shown that RNA silencing does not spread systemically to non-co-transformed (lateral) roots and only inef®ciently to the non-transgenic shoot. Furthermore, evidence is presented which shows that RNAi is cell autonomous in the root epidermis. Key words: A. rhizogenes, Arabidopsis, Medicago truncatula, RNAi, roots, silencing, systemic spreading

High Salt Levels Reduced Dissimilarities in Root-Associated Microbiomes of Two Barley Genotypes

Plants harbor in and at their roots bacterial microbiomes that contribute to their health and fitness. The microbiome composition is controlled by the environment and plant genotype. Previously, it was shown that the plant genotype-dependent dissimilarity of root microbiome composition of different species becomes smaller under drought stress. However, it remains unknown whether this reduced plant genotype-dependent effect is a specific response to drought stress or a more generic response to abiotic stress. To test this, we studied the effect of salt stress on two distinct barley (Hordeum vulgare L.) genotypes: the reference cultivar Golden Promise and the Algerian landrace AB. As inoculum, we used soil from salinized and degraded farmland on which barley was cultivated. Controlled laboratory experiments showed that plants inoculated with this soil displayed growth stimulation under high salt stress (200 mM) in a plant genotype-independent manner, whereas the landrace AB also showed significant growth stimulation at low salt concentrations. Subsequent analysis of the root microbiomes revealed a reduced dissimilarity of the bacterial communities of the two barley genotypes in response to high salt, especially in the endophytic compartment. High salt level did not reduce α-diversity (richness) in the endophytic compartment of both plant genotypes but was associated with an increased number of shared strains that respond positively to high salt. Among these, Pseudomonas spp. were most abundant. These findings suggest that the plant genotype-dependent microbiome composition is altered generically by abiotic stress.[Formula: see text

Additional file 2: of A genetically and functionally diverse group of non-diazotrophic Bradyrhizobium spp. colonizes the root endophytic compartment of Arabidopsis thaliana

Table S2. Assembly statistics (XLSX 11 kb