Plant Ageing, a Counteracting Agent to Xenobiotic Stress

International audienc

Nemesia Root Hair Response to Paper Pulp Substrate for Micropropagation

Agar substrates for in vitro culture are well adapted to plant micropropagation, but not to plant rooting and acclimatization. Conversely, paper-pulp-based substrates appear as potentially well adapted for in vitro culture and functional root production. To reinforce this hypothesis, this study compares in vitro development of nemesia on several substrates. Strong differences between nemesia roots growing in agar or in paper-pulp substrates were evidenced through scanning electron microscopy. Roots developed in agar have shorter hairs, larger rhizodermal cells, and less organized root caps than those growing on paper pulp. In conclusion, it should be noted that in this study, in vitro microporous substrates such as paper pulp lead to the production of similar root hairs to those found in greenhouse peat substrates. Consequently, if agar could be used for micropropagation, rooting, and plant acclimatization, enhancement could be achieved if rooting stage was performed on micro-porous substrates such as paper pulp

Trends in SAVR with biological vs. mechanical valves in middle-aged patients: results from a French large multi-centric survey

Background/introductionCurrently, despite continued issues with durability ( 1), biological prosthetic valves are increasingly chosen over mechanical valves for surgical aortic valve replacement (SAVR) in adult patients of all ages, at least in Western countries. For younger patients, this choice means assuming the risks associated with a redo SAVR or valve-in-valve procedure.PurposeTo assess the use of mechanical vs. biological valve prostheses for SAVR relative to patient's age and implant time in a large population extracted from the French National Database EPICARD.MethodsPatients in EPICARD undergoing SAVR from 2007 to 2022 were included from 22 participating public or private centers chosen to represent a balanced representation of centre sizes and geographical discrepancies. Patients with associated pathology of the aorta (aneurysm or dissection) and requiring a vascular aortic prosthesis were excluded. Comparisons were made amongst centers, valve choice, implant date range, and patient age.ResultsWe considered 101,070 valvular heart disease patients and included 72,375 SAVR (mean age 71.4 ± 12.2 years). We observed a mechanical vs. biological prosthesis ratio (MBPR) of 0.14 for the overall population. Before 50 years old (y-o), MBPR was >1.3 (p < 0.001) while patients above 60 years-old received principally biological SAVR (p < 0.0001). Concerning patients between 50 and 60 years-old patients, MPVR was 1.04 (p = 0.03). Patients 50–60 years-old from the first and second study duration quartile (before August 2015) received preferentially mechanical SAVR (p < 0.001). We observed a shift towards more biological SAVR (p < 0.001) for patients from the third and fourth quartile to reach a MBPR at 0.43 during the last years of the series. Incidentally, simultaneous mitral valve replacement were more common in case of mechanical SAVR (p < 0.0001), while associated CABGs were more frequent in case of biological SAVR (p < 0.0001).ConclusionIn a large contemporary French patient population, real world practice showed a recent shift towards a lower age-threshold for biological SAVR as compared to what would suggest contemporary guidelines

Heavy-Metal Attack on Freshwater Side: Physiological Defense Strategies of Macrophytes and Ecotoxicological Ops

International audienceFor many years, strong anthropogenic pollutions like heavy metals induce deep changes in all ecosphere compartments especially in streams where deleterious effects on aquatic plants are noted. Indeed, ionic interactions on whole plant surface and permanent replacement of metal pool lead to ecophysiological disruptions among freshwater macrophytes. To prevent from irreversible alterations, macrophytes develop a typical antioxidant systems (e.g., proteins, secondary metabolites, metabolic pathways) to protect intracellular components from reactive oxygen species and to preserve major biosynthesis pathways like photosynthesis. These macrophytes also accumulate solutes to cope with increasing external metal toxicity. Moreover, new anatomical features reducing water stress and leading to cell homeostasis can appear in leaves, as a double endodermis. Tolerance to heavy metals is an interesting feature of freshwater plants for understanding any adaptation and acclimation processes to highly ionic concentrated environments at the genetic level. Indeed, specific genes involved in the synthesis of molecular chaperones might be related to heavy-metal tolerance in macrophytes. Due to their metal sensitivity and bioaccumulation capabilities, these organisms appear essential in ecotoxicological studies like biomonitoring to manage natural habitats

Contribution à l'étude de la résistance de différents génotypes d'HELIANTHUS (Astéracées) à Orobanche cumana Wallr. (Orobanchacées)

Le criblage de nombreux Helianthus, sauvages, hybrides et lignées, a été effectué en serre afin de sélectionner des génotypes résistants à Orobanche cumana. Une étude plus approfondie de ces génotypes a montré que le génotype LR1 descendant du croisement d'un tournesol cultivé avec l'espèce sauvage H. debilis debilis, induit des nécroses du parasite conduisant à une réduction drastique du nombre d'orobanches émergées. Le génotype 92B6 issu du croisement interspécifique avec l'espèce sauvage H. argophyllus provoque lui aussi de nombreuses nécroses mais à des stades plus tardifs du développement de l'orobanche qui ne parvient toutefois pas à la floraison. Un système de culture hydroponique du couple tournesol / orobanche a permis d'étudier les réactions de défense chez le génotype résistant LRI. La réponse de ce génotype fait intervenir des épaississements de paroi, l'occlusion des vaisseaux du xylène et des divisions cellulaires au niveau du parenchyme cortical et du phloème. Ces réactions conduisent à une diminution de l'alimentation en eau et en nutriments du parasite. En effet, l'importation d'assimilats marqués au 14C dans les orobanches fixées sur les racines du génotype résistant LR1 est réduite par rapport à celle observée chez les orobanches se développant sur un tournesol sensible.In order to find broomrape resistant Helianthus genotypes a screening of numerous wild, hybrids, lines and varieties was carried out under glasshouse conditions. A more accurate study of the most interesting genotypes shows that H. debilis debilis-215 x H. annuus derived genotype (LR1) induces parasite necrosis leading to a decrease in broomrape emergence and flowering.NANTES-BU Sciences (441092104) / SudocSudocFranceF

The most powerful multivariate normality test for plant genomics and dynamics data sets

International audienceData analysis methods like analysis of variance and regression in plant sciences depend on the assumption that the biological data are normal. Using a normality test is the best way to check whether the distribution is normal or not. Plant genomic and dynamic studies generate data with leptokurtic distribution and the most appropriate normality test is the Shapiro-Francia one. However multivariate extensions of this test have not been designed yet and plant data matrix cannot be performed efficiently or without bias. Thus, our analysis focused on the development of an easy-using algorithm to extend the application of the Shapiro-Francia test to multivariate data matrix in plant studies

Myriophyllum alterniflorum biochemical changes during in vitro Cu/Cd metal stress: Focusing on cell detoxifying enzymes

International audienceGiven the toxicity of trace metals, their concentration, speciation and bioavailability serve to induce various plant detoxification processes, which themselves are specific to several parameters like plant species, tissue type and developmental stage. In this study, Myriophyllum alterniflorum (or alternate watermilfoil) enzyme activities (ascorbate peroxidase, catalase, glutathione peroxidase and superoxide dismutase) from in vitro cultures was measured over 27 days in response to copper (Cu) or cadmium (Cd) stress. These enzymes are unique to reactive oxygen species (ROS) scavenging (mainly hydrogen peroxide H2O2 and superoxide anion O2•−) and moreover showed specific or unspecific activity profiles, depending on the metal concentrations used. Our results suggest a higher-priority protection of chloroplasts during the initial days of exposure to both metals. At the same time, the increased catalase activity could indicate an H2O2 diffusion in peroxisome in order to protect other organelles from ROS accumulation. However, as opposed to the Cd effects, high Cu concentrations appear to induce a “limited oxidative threshold” for some antioxidant enzymes, which could suggest an ion absorption competition between Cu2+ and Fe2+. In spite of an overall analysis conducted of the scavenging processes occurring in plant cells, biochemical analyses still yielded relevant indications regarding the watermilfoil strategies used for ROS management

Stream rehabilitation with Myriophyllum alterniflorum: micropropagation and heavy-metal hyperaccumulation

International audienceNowadays, submersed aquatic macrophytes play a key role in stream ecology and they are often used as biomonitors of freshwater quality. So, these plants appear as natural candidates to stream rehabilitation experiments. Among them, the stream macrophyte Myriophyllum alterniflorum is used recently as biomonitor and is potentially useful for the restoration of heavy-metal contaminated localities. The best way to obtain a mass production of watermilfoil plants is micropropagation. Micropropagated clones were acclimatized in a synthetic medium and in situ reintroduction was performed efficiently. This is the first report of micropropagated-plant transplantation in streams. The successful establishment of watermilfoil beds even in polluted areas strongly suggested that ecological restoration using micropropagated watermilfoil is a promising biotechnology for phytoremediation and rehabilitation of degraded areas. Moreover, high bioconcentration factors evidenced that watermilfoil hyperaccumulates Cd and Cu, and could be a potential tool in phytoremediation studies

Mineral nutrient concentration influences sunflower infection by broomrape (Orobanche cumana)

L'Orobanche cumana Wallr., plante parasite racinaire, provoque de nombreux dégâts sur les cultures de tournesol (Helianthus annuus L.) dans toute l'Europe. Jusqu'à aujourd'hui, la seule méthode de lutte efficace reste l'utilisation de génotypes résistants. Cependant, les mécanismes de résistance à l'orobanche restent encore méconnus, bien que des études précédentes aient démontré l'existence de plusieurs mécanismes. L'étude de génotypes de tournesol sensible (2603) et résistant (LR1) en culture hydroponique a permis de mettre en évidence que la concentration du milieu de culture modifie le niveau d'infestation du tournesol par l'orobanche. Pour le génotype sensible (2603), le nombre de parasites nécrosés augmente avec la concentration du milieu de culture. Pour le génotype résistant (LR1), l'augmentation de la concentration du milieu de culture diminue l'infestation en diminuant le nombre d'orobanches fixées sur les racines et en limitant leur développement ultérieur. Lorsque l'on cultive les tournesols dans le milieu non dilué, l'allocation de radiocarbone dans la plante se modifie avec un accroissement de la force puits de l'apex caulinaire, alors que l'incorporation de 14C est réduite dans les orobanches. Notre étude démontre qu'en milieu contrôlé, la concentration en nutriments influe directement sur le potentiel de résistance du tournesol à l'orobanche

Use of Myriophyllum alterniflorum (Haloragaceae) for restoration of heavy-metal-polluted freshwater environments: preliminary results

International audienceMyriophyllum alterniflorum D.C., a poor-known aquatic macrophyte native to north-European freshwaters, was found even in polluted environments from the Vienne river and its tributaries which are often loaded with cadmium and copper near the Limoges metropolis (Haute-Vienne, France). This plant could cope with, to some extent, heavy-metal pollution and is used as a bioindicator since 2009. For these reasons, M. alterniflorum appears as a good candidate for running-freshwater restoration. In this way, the in vitro culture of this plant species was developed to allow a mass production and to study its phytoaccumulation capabilities. The in vitro culture of M. alterniflorum was optimized using Murashige & Skoog's medium allowing rapid growth and biomass production. Phytoaccumulation tests indicate that this species accumulate rapidly heavy metal as a 415-fold increase of cadmium and a 32-fold increase of copper were evidenced on the first 24h after contamination. Moreover, preliminary results concerning the reintroduction of M. alterniflorum clones in degraded and non-polluted areas are also rather encouraging, indicating that this taxon is a good candidate to freshwater restoration