An Arabidopsis thaliana arabinogalactan-protein (AGP31) and several cationic AGP fragments catalyse the boron bridging of rhamnogalacturonan-II

Rhamnogalacturonan-II (RG-II) is a complex pectic domain in plant primary cell walls. In vivo, most RG-II domains are covalently dimerised via borate diester bridges, essential for correct cell-wall assembly, but the dimerisation of pure RG-II monomers by boric acid in vitro is extremely slow. Cationic ‘chaperones’ can promote dimerisation, probably by overcoming the mutual repulsion between neighbouring anionic RG-II molecules. Highly effective artificial chaperones include Pb(2+) and polyhistidine, but the proposed natural chaperones remained elusive. We have now tested cationic peptide fragments of several Arabidopsis thaliana arabinogalactan-proteins (AGPs) as candidates. Fragments of AGP17, 18, 19 and 31 were effective, typically at ∼25 µg/ml (9–19 µM), promoting the boron bridging of 16–20 µM monomeric RG-II at pH 4.8 in vitro. Native AGP31 glycoprotein was also effective, and hexahistidine was moderately so. All chaperones tested interacted reversibly with RG-II and were not consumed during the reaction; thus they acted catalytically, and may constitute the first reported boron-acting enzyme activity, an RG-II borate diesterase. Many of the peptide chaperones became less effective catalysts at higher concentration, which we interpret as due to the formation of RG-II–peptide complexes with a net positive charge, as mutually repulsive as negatively charged pure RG-II molecules. The four unique AGPs studied here may serve an enzymic role in the living plant cell, acting on RG-II within Golgi cisternae and/or in the apoplast after secretion. In this way, RG-II and specific AGPs may contribute to cell-wall assembly and hence plant cell expansion and development

Beyond purified dietary fibre supplements : compositional variation between cell wall fibre from different plants influences human faecal microbiota activity and growth in vitro

Funding Michael Solvang was funded by a Scottish Government Rural and Environment Science & Analytical Services (RESAS) PhD studentship and Freda Farquharson, Graham Horgan, Wendy Russell and Petra Louis also received financial support from RESAS. The authors would like to acknowledge the support of the Maxwell Compute Cluster funded by the University of Aberdeen.Peer reviewedPublisher PD

Enzymically attaching oligosaccharide-linked ‘cargoes’ to cellulose and other commercial polysaccharides via stable covalent bonds

International audienc

Cuantificacion en el uso y determinacion de la percepcion del efecto del bromuro de metilo en la VII Region

Resumen (Spanish, English)91 p.En la Séptima Región se realizó una encuesta a encargados de Viveros o Invernaderos, para verificar el proceso de adaptación de la población a una nueva tecnología en el tratamiento de sustrato, con el fin de cuantificar el consumo actual de Bromuro de Metilo y determinar la percepción que se tiene del efecto de este producto en el ecosistema. A través de las encuestas aplicadas se identificaron distintos factores tales como, cantidad empleada, uso, concentración utilizada, modo de aplicación e incluso en forma específica contra qué tipo de insectos, hongos, y malezas se aplica, así como también, si están informados de su pronta eliminación del mercado. De acuerdo al Protocolo de Montreal (Copenhague, Noviembre 1992), el Bromuro de Metilo tiene un plazo de eliminación: en el año 2005, en los países desarrollados, y en el año 2015, en los países en desarrollo. En consecuencia, al ser Chile un país exportador a países desarrollados se ve obligado a encontrar rápidamente (antes del año 2005), formas viables para cumplir con estas exigencias. Los resultados obtenidos confirman la necesidad de encontrar y entregar información de las diversas alternativas al Bromuro de Metilo, para que esta Región no se vea afectada por la eliminación de este producto. El común de los agricultores sólo usa para la desinfección el Bromuro de Metilo (49%), mientras que otros no desinfectan suelo(51%), ya que utilizan sustratos previamente desinfectados o bien emplean el suelo que ellos tienen por no estar contaminado, confiados en el análisis realizado por el SAG. La mayoría de los agricultores, tanto de Viveros como Invernaderos, no conoce (61%) y no utiliza (100%) otros productos para desinfectar suelo a parte del Bromuro de Metilo

Active proton efflux, nutrient retention and boron-bridging of pectin are related to greater tolerance of proton toxicity in the roots of two <i>Erica </i>species

36 páginas.-- 6 figuras.-- 2 tablas.-- 50 referencias.-- Appendix A. The supplementary data related to this article is https://doi.org/10.1016/j.plaphy.2018.02.029Background and aims: Tolerance to soil acidity was studied in two species of Ericaceae that grow in mine-contaminated soils (S Portugal, SW Spain) to find out if there are interspecific variations in H+ tolerance which might be related to their particular location. Methods: Tolerance to H+ toxicity was tested in nutrient solutions using seeds collected in SW Spain. Plant growth and nutrient contents in leaves, stems and roots were determined. Viability tests and proton exchange were studied in roots exposed, short-term, to acidic conditions. Membrane ATPase activity and the cell-wall pectic polysaccharide domain rhamnogalacturonan-II (RG-II) were analysed to find out interspecific differences. Results: Variation in survival, growth and mineral composition was found between species. The H+-tolerant species (Erica andevalensis) showed greater concentration of nutrients than E. australis. Very low pH (pH 2) produced a significant loss of root nutrients (K, P, Mg) in the sensitive species. Root ATPase activity was slightly higher in the tolerant species with a correspondingly greater H+ efflux capacity. In both species, the great majority of the RG-II domains were in their boron-bridged dimeric form. However, shifting to a medium of pH 2 caused some of the boron bridges to break in the sensitive species. Conclusions: Variation in elements linked to the cell wall-membrane complex and the stability of their components (RG-II, H+-ATPases) are crucial for acid stress tolerance. Thus, by maintaining root cell structure, active proton efflux avoided toxic H+ build-up in the cytoplasm and supported greater nutrient acquisition in H+-tolerant species.This work was partially granted by MICINN contract CGL2006/02860 and by Fundación Areces. SCF thanks the BBSRC (UK; grant reference BB/H000690/1) and DS thanks the Comisión Nacional de Investigación Científica y Tecnológia (Conicyt; Chile) for financial support.Peer reviewe

High-density genetic map and QTL analysis of soluble solid content, maturity date, and mealiness in peach using genotyping by sequencing

Peach (Prunus persica) is one of the most important temperate fruit trees in the world, based on its production and cultivated area. Consumer acceptance is the principal objective of multiple breeding programs and it is dependent on many factors. Among these factors, an important role is played by the soluble solids content (SSC) and the postharvest performance represented by mealiness (M) susceptibility as a chilling injury disorder. Additionally, a major maturity date (MD) QTL has been reported to have a pleiotropic effect on both M and SSC. The aim of this work was QTL identification of SSC, MD, and M and to identify adequate candidate genes that are linked to regulation of these traits. The analysis was performed by evaluation of fruit quality traits during three consecutive seasons in an F1 progeny of 194 siblings, which were obtained from the intraspecific cross between the yellow-flesh peach “O’Henry” and the white-flesh nectarine NR-053. The main result was the construction of a genetic linkage map with 499 markers (486 SNPs, 11 SSRs, and two morphological markers) spanning 717.6 cM, with an average distance between markers of 1.5 cM/cluster. The analysis allowed the identification of consistent QTLs for SSC and M in the linkage group LG5 and for MD in LG1, LG2, LG5, and LG6. A large number of genes were annotated in QTL intervals, which was reduced by selecting the genes with at least one SNP, which caused an amino acid variation. For SSC, the data identified four transcription factors, one gene involved directly with the sugar accumulation process, and one cell wall remodeling-related gene. For MD, 23 cell wall-related genes, three jasmonic acid-linked genes, eight transcription factors, and one ripening-related gene were identified. Finally, only one cell wall gene was identified that was associated with M. In conclusion, these results improve our understanding of the genetic control of fruit quality traits with commercial relevance in P. persica and specifically in the O × N mapping population.info:eu-repo/semantics/publishedVersio

Identification of DNA Methylation and Transcriptomic Profiles Associated With Fruit Mealiness in Prunus persica (L.) Batsch

Peach (Prunus persica) fruits have a fast ripening process and a shelf-life of days, presenting a challenge for long-distance consuming markets. To prolong shelf-life, peach fruits are stored at low temperatures (0 to 7 °C) for at least two weeks, which can lead to the development of mealiness, a physiological disorder that reduces fruit quality and decreases consumer acceptance. Several studies have been made to understand this disorder, however, the molecular mechanisms underlying mealiness are not fully understood. Epigenetic factors, such as DNA methylation, modulate gene expression according to the genetic background and environmental conditions. In this sense, the aim of this work was to identify differentially methylated regions (DMRs) that could affect gene expression in contrasting individuals for mealiness. Peach flesh was studied at harvest time (E1 stage) and after cold storage (E3 stage) for 30 days. The distribution of DNA methylations within the eight chromosomes of P. persica showed higher methylation levels in pericentromeric regions and most differences between mealy and normal fruits were at Chr1, Chr4, and Chr8. Notably, differences in Chr4 co-localized with previous QTLs associated with mealiness. Additionally, the number of DMRs was higher in CHH cytosines of normal and mealy fruits at E3; however, most DMRs were attributed to mealy fruits from E1, increasing at E3. From RNA-Seq data, we observed that differentially expressed genes (DEGs) between normal and mealy fruits were associated with ethylene signaling, cell wall modification, lipid metabolism, oxidative stress and iron homeostasis. When integrating the annotation of DMRs and DEGs, we identified a CYP450 82A and an UDP-ARABINOSE 4 EPIMERASE 1 gene that were downregulated and hypermethylated in mealy fruits, coinciding with the co-localization of a transposable element (TE). Altogether, this study indicates that genetic differences between tolerant and susceptible individuals is predominantly affecting epigenetic regulation over gene expression, which could contribute to a metabolic alteration from earlier stages of development, resulting in mealiness at later stages. Finally, this epigenetic mark should be further studied for the development of new molecular tools in support of breeding programs

An Arabidopsis thaliana arabinogalactan-protein (AGP31) and several cationic AGP fragments catalyse the boron bridging of rhamnogalacturonan-II

International audienceRhamnogalacturonan-II (RG-II) is a complex pectic domain in plant primary cell walls. In vivo, most RG-II domains are covalently dimerised via borate diester bridges, essential for correct cell-wall assembly, but the dimerisation of pure RG-II monomers by boric acid in vitro is extremely slow. Cationic ‘chaperones’ can promote dimerisation, probably by overcoming the mutual repulsion between neighbouring anionic RG-II molecules. Highly effective artificial chaperones include Pb2+ and polyhistidine, but the proposed natural chaperones remained elusive. We have now tested cationic peptide fragments of several Arabidopsis thaliana arabinogalactan-proteins (AGPs) as candidates. Fragments of AGP17, 18, 19 and 31 were effective, typically at ~25 µg/ml (9–19 µM), promoting the boron bridging of 16–20 µM monomeric RG-II at pH 4.8 in vitro. Native AGP31 glycoprotein was also effective, and hexahistidine was moderately so. All chaperones tested interacted reversibly with RG-II and were not consumed during the reaction; thus they acted catalytically, and may constitute the first reported boron-acting enzyme activity, an RG-II borate diesterase. Many of the peptide chaperones became less effective catalysts at higher concentration, which we interpret as due to the formation of RG-II–peptide complexes with a net positive charge, as mutually repulsive as negatively charged pure RG-II molecules. The four unique AGPs studied here may serve an enzymic role in the living plant cell, acting on RG-II within Golgi cisternae and/or in the apoplast after secretion. In this way, RG-II and specific AGPs may contribute to cell-wall assembly and hence plant cell expansion and development