Disentangling pectic homogalacturonan and rhamnogalacturonan-I polysaccharides: Evidence for sub-populations in fruit parenchyma systems

The matrix polysaccharides of plant cell walls are diverse and variable sets of polymers influencing cell wall, tissue and organ properties. Focusing on the relatively simple parenchyma tissues of four fruits – tomato, aubergine, strawberry and apple – we have dissected cell wall matrix polysaccharide contents using sequential solubilisation and antibody-based approaches with a focus on pectic homogalacturonan (HG) and rhamnogalacturonan-I (RG-I). Epitope detection in association with anion-exchange chromatography analysis indicates that in all cases solubilized polymers include spectra of HG molecules with unesterified regions that are separable from methylesterified HG domains. In highly soluble fractions, RG-I domains exist in both HG-associated and non-HG-associated forms. Soluble xyloglucan and pectin-associated xyloglucan components were detected in all fruits. Aubergine glycans contain abundant heteroxylan epitopes, some of which are associated with both pectin and xyloglucan. These profiles of polysaccharide heterogeneity provide a basis for future studies of more complex cell and tissue systems

Monoclonal antibodies indicate low-abundance links between heteroxylan and other glycans of plant cell walls.

The derivation of two sensitive monoclonal antibodies directed to heteroxylan cell wall polysaccharide preparations has allowed the identification of potential inter-linkages between xylan and pectin in potato tuber cell walls and also between xylan and arabinogalactan-proteins in oat grain cell walls. Plant cell walls are complex composites of structurally distinct glycans that are poorly understood in terms of both in muro inter-linkages and developmental functions. Monoclonal antibodies (MAbs) are versatile tools that can detect cell wall glycans with high sensitivity through the specific recognition of oligosaccharide structures. The isolation of two novel MAbs, LM27 and LM28, directed to heteroxylan, subsequent to immunisation with a potato cell wall fraction enriched in rhamnogalacturonan-I (RG-I) oligosaccharides, is described. LM27 binds strongly to heteroxylan preparations from grass cell walls and LM28 binds to a glucuronosyl-containing epitope widely present in heteroxylans. Evidence is presented suggesting that in potato tuber cell walls, some glucuronoxylan may be linked to pectic macromolecules. Evidence is also presented that suggests in oat spelt xylan both the LM27 and LM28 epitopes are linked to arabinogalactan-proteins as tracked by the LM2 arabinogalactan-protein epitope. This work extends knowledge of the potential occurrence of inter-glycan links within plant cell walls and describes molecular tools for the further analysis of such links.This work was supported by the European Union Seventh Framework Programme (FP7 2007-2013) under the WallTraC project (Grant Agreement number 263916). (This article reflects the authors’ views only and the European Union is not liable for any use that may be made of the information contained herein). The work was also supported by the United Kingdom Biotechnology and Biological Research Council (BBSRC, Grant BB/K017489/1). JX acknowledges support from the Chinese Scholarship Council, TAT from a BBSRC studentship and MGR from the Danish Strategic Research Council and The Danish Council for Independent Research, Technology and Production Sciences as part of the GlycAct project (FI 10-093465). We acknowledge kind gifts of enzymes from Harry Gilbert and oligosaccharides from Sanna Koutaniemi. We thank Theodora Tryfona for mass spectrometry analysis.This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s00425-015-2375-

Comparative in situ analyses of cell wall matrix polysaccharide dynamics in developing rice and wheat grain

Cell wall polysaccharides of wheat and rice endosperm are an important source of dietary fibre. Monoclonal antibodies specific to cell wall polysaccharides were used to determine polysaccharide dynamics during the development of both wheat and rice grain. Wheat and rice grain present near synchronous developmental processes and significantly different endosperm cell wall compositions, allowing the localisation of these polysaccharides to be related to developmental changes. Arabinoxylan (AX) and mixed-linkage glucan (MLG) have analogous cellular locations in both species, with deposition of AX and MLG coinciding with the start of grain filling. A glucuronoxylan (GUX) epitope was detected in rice, but not wheat endosperm cell walls. Callose has been reported to be associated with the formation of cell wall outgrowths during endosperm cellularisation and xyloglucan is here shown to be a component of these anticlinal extensions, occurring transiently in both species. Pectic homogalacturonan (HG) was abundant in cell walls of maternal tissues of wheat and rice grain, but only detected in endosperm cell walls of rice in an unesterified HG form. A rhamnogalacturonan-I (RG-I) backbone epitope was observed to be temporally regulated in both species, detected in endosperm cell walls from 12 DAA in rice and 20 DAA in wheat grain. Detection of the LM5 galactan epitope showed a clear distinction between wheat and rice, being detected at the earliest stages of development in rice endosperm cell walls, but not detected in wheat endosperm cell walls, only in maternal tissues. In contrast, the LM6 arabinan epitope was detected in both species around 8 DAA and was transient in wheat grain, but persisted in rice until maturity

Molecular and biochemical tools for plant cell wall glycan analysis

Plant cell walls are complex structures composed of diverse polymers: polysaccharides, proteins and sometimes phenolic compounds, varying in nature, structure and length. A study of the structure and occurrence of cell wall polysaccharides is required to be able to understand their mechanical and biological functions as well as to understand the overall architecture of cell walls. Studying cell wall polysaccharides is challenging mostly because of the limited methods and tools available for their characterisation. Chromatography systems are often used to separate and purify cell wall polysaccharides. In parallel, monoclonal antibodies (mAbs) have been largely used to study cell wall polysaccharide localisation, compositional variation and their potential mechanical properties and biological functions. However, the number of epitopes currently targeted by mAbs is limited and some polysaccharide features cannot be studied using mAbs. The project reported here was focused on the development of new methods, namely Epitope Detection Chromatography and glycan sandwich-ELISA, as well as the raising and characterisation of several new monoclonal antibodies PDT2, PDT5, PDT8, PDT10, PDT13 and PDT17. These new probes recognise various RG-I (PDT10, PDT13), AGP (PDT8, PDT17) and heteroxylan (PDT2, PDT5) specific epitopes. The Epitope Detection Chromatography can perform high resolution glycan analysis by combining the separation of polysaccharides by chromatography and their detection by specific molecular probes such as monoclonal antibodies and carbohydrate-binding modules. Contrary to numerous available polysaccharide analysis techniques EDC analysis can be performed directly on complex mixtures such as cell wall extracts and target one precise defined oligosaccharide or epitope. The development of sandwich-ELISA allows the study of multi-component complexes and inter-linked polysaccharides. The two methods can be combined to study subsets of polysaccharides. Here, the two techniques have been used together with the new set of PDT monoclonal antibodies to study cell wall polysaccharide composition and multi-polysaccharide complexes in a range of biological systems: tobacco seed endosperm, grape fruit and Arabidopsis thaliana. These studies have led to the identification of RG-I sub-families in tobacco seed and A. thaliana, as well as potential xylan-pectin linkages found in A. thaliana stem cell walls

Épidémiologie de listériose néonatale de 1987 à 2001 (étude rétrospective cas-témoins des paramètres en faveur de listériose à la naissance)

La listériose est l'une des trois principales causes d'infection materno-fœtale. Le but de notre travail était de mettre en évidence des éléments d'orientation vers le diagnostic de listériose lors d'une infection materno-foetale et d'étudier l'incidence des séquelles neurologiques qui paraissait plus importante avec cette infection dans une série récente. .....Les autres paramètres étudiés ( menace d'accouchement prématuré, détresse respiratoire, troubles hémodynamiques, pH à l'admission, séquelles neurologiques ) ne montraient pas de différence significative. Ainsi, la survenue de signes de souffrance foetale aiguë dans un contexte fébrile doit faire évoquer une listériose néonatale.NANTES-BU Médecine pharmacie (441092101) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF