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Mont-Saint-Aignan, France

Plancot B.,University of Rouen | Santaella C.,Aix - Marseille University | Jaber R.,University of Rouen | Kiefer-Meyer M.C.,University of Rouen | And 6 more authors.
Plant Physiology

Plant pathogens including fungi and bacteria cause many of the most serious crop diseases. The plant innate immune response is triggered upon recognition of microbe-associated molecular patterns (MAMPs) such as flagellin22 and peptidoglycan. To date, very little is known of MAMP-mediated responses in roots. Root border cells are cells that originate from root caps and are released individually into the rhizosphere. Root tips of Arabidopsis (Arabidopsis thaliana) and flax (Linum usitatissimum) release cells known as "border-like cells." Whereas root border cells of pea (Pisum sativum) are clearly involved in defense against fungal pathogens, the function of border-like cells remains to be established. In this study, we have investigated the responses of root border-like cells of Arabidopsis and flax to flagellin22 and peptidoglycan. We found that both MAMPs triggered a rapid oxidative burst in root border-like cells of both species. The production of reactive oxygen species was accompanied by modifications in the cell wall distribution of extensin epitopes. Extensins are hydroxyproline-rich glycoproteins that can be cross linked by hydrogen peroxide to enhance the mechanical strength of the cell wall. In addition, both MAMPs also caused deposition of callose, a well-known marker of MAMP-elicited defense. Furthermore, flagellin22 induced the overexpression of genes involved in the plant immune response in root border-like cells of Arabidopsis. Our findings demonstrate that root borderlike cells of flax and Arabidopsis are able to perceive an elicitation and activate defense responses. We also show that cell wall extensin is involved in the innate immunity response of root border-like cells. © 2013 American Society of Plant Biologists. All Rights Reserved. Source

Riah-Anglet W.,Unite AgriTerr | Trinsoutrot-Gattin I.,Unite AgriTerr | Martin-Laurent F.,CNRS Agroecology Lab | Laroche-Ajzenberg E.,Unite AgriTerr | And 3 more authors.
Applied Soil Ecology

Links between the microbial community structure and soil functions are unclear. The study of these relationships requires the development of highly specific experimental approaches. In this work, the soil microbial community structure and function relationship was evaluated in relation to heat stress in a soil microcosm incubated at 17. °C and 50. °C. We selected a luvisol that included two land uses. Samples were taken from the soil of a long-term (>10 year) arable cropping plot (CC) and a permanent grassland (PG) (>25 years). The soil functions were evaluated by measuring the enzyme activities, including cellulase, N-acetyl-glucosaminidase, β-glucosidase, xylanase and dehydrogenase. The total microbial biomass was assayed by the quantification of the total DNA extracted from the microcosm soils. The abundance of total bacterial and fungal communities and different bacterial taxa were measured by qPCR rRNA genes. For both soil types, heat stress induced changes in the microbial community structure and soil functions. In most cases, the results yielded effects following heat treatment. All of the enzymes were inhibited except xylanase. Heat stress significantly reduced the total microbial biomass and fungal abundance in the soils. The abundance of the total bacterial community was not affected by heat stress. In the two soils, the dominant taxa were Actinobacteria (13-40%) and Bacteroidetes (14-32%), while Planctomycetes and Gammaproteobacteria exhibited lower abundance (0-3%). Changes in the microbial community structure and changes in the functions were correlated; the correlation was positive in the PG soil and negative in the CC soil. The changes in the CC soil structural and functional state were greater than of those observed in PG soil. Our initial hypothesis was confirmed, indeed, grassland soil is more resistant to drastic stress due to its highly abundant and highly diversified microbial community. These results represent a contribution to the understanding of soil microbial community structure and functions relationships. © 2014 Elsevier B.V. Source

Riah W.,Unite AgriTerr | Laval K.,Unite AgriTerr | Laroche-Ajzenberg E.,Unite AgriTerr | Mougin C.,French National Institute for Agricultural Research | And 2 more authors.
Environmental Chemistry Letters

The use of pesticides in agriculture has highly increased during the last 40 years to increase crop yields. However, today most pesticides are polluting water, soil, atmosphere and food. Pesticides are also impact soil enzymes, which are essential catalysts ruling the quality of soil life. In particular, the activity of soil enzymes control nutrient cycles, and, in turn, fertilization. Here, we review the effects of pesticides on the activity of soil enzymes in terrestrial ecosystems. Enzymes include dehydrogenase, fluorescein diacetate hydrolase, acid phosphatase, alkaline phosphatase, phosphatase, β-glucosidase, cellulase, urease and aryl-sulfatase. Those enzymes are involved in the cycles of carbon, nitrogen, sulfur and phosphorus. The main points of our analysis are (1) the common inhibition of dehydrogenase in 61 % of studies, stimulation of cellulase in 56 % of studies and no response of aryl-sulfatase in 67 % of studies. (2) Fungicides have mainly negative effects on enzymatic activities. (3) Insecticides can be classified into two groups, the first group represented by endosulfan having an overall positive impact while the second group having a negative effect. (4) Herbicides can be classified into two groups, one group with few positive effect and another group with negative effect. © 2014 Springer International Publishing Switzerland. Source

Gangneux C.,Unite AgriTerr | Cannesan M.-A.,Unite AgriTerr | Cannesan M.-A.,University of Rouen | Bressan M.,Unite AgriTerr | And 6 more authors.

Aphanomyces euteiches is a widespread oomycete pathogen causing root rot in a wide range of leguminous crops. Losses can reach up to 100% for pea culture and there is currently no registered pesticide for its control. Crop management remains the most efficient tool to control root rot, and avoidance of infested soil seems to be the optimal solution. A test was developed to identify fields suitable for pea crops, consisting of the determination of the inoculum potential of soil using baiting plants. A new rapid, specific, and sensitive molecular method is described allowing the quantification of less than 10 oospores per gram of soil. This challenge is achieved by a real-time polymerase chain reaction procedure targeting internal transcribed spacer 1 from the ribosomal DNA operons. A preliminary study based on typical soils from northwestern France demonstrated that the A. euteiches oospore density in soil is related to the inoculum potential. Furthermore, this method has proved sensitive enough to accurately study the influence of biotic factors that may govern the actual emergence of root rot. © 2014 The American Phytopathological Society. Source

Alix S.,Unite AgriTerr | Mahieu A.,Unite AgriTerr | Terrie C.,Unite AgriTerr | Soulestin J.,Ecole Des Mines de Douai | And 6 more authors.
European Polymer Journal

Within the recent years, researches dealing with the applications of intelligent and active packaging for food applications have taken a great importance. Intelligent packaging-systems are used to inform and advertise the consumers by giving information on the food quality during transport and storage. Active packaging-systems have also acquired new functions as antimicrobials and/or oxygen or water scavenging activities by incorporating active molecules. The aim of these packaging is to maintain or extend the quality and shelf-life of the food element. The application of this strategy, concerning bio-sourced packaging, is recent. In this work, polycaprolactones were blended in a starch based matrix to improve the suitability for contact with food of the packaging and to obtain a modulated water-scavenger effect. The migration of PCL in the pseudo-multilayered and multilayered films was investigated by FT-IR. Moreover, chitosan was included in the formulation to reduce the bacterial adhesion potential on the packaging. © 2013 Elsevier B.V. All rights reserved. Source

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