Comparaison de la nutrition minérale du mil (Pennisetum glaucum L.R. Br.) en présence de stress hydrique et de stress salin

Objectif : L'amélioration de l’efficience de l’irrigation en s’orientant vers la détermination des besoins réels en eau des différentes cultures et aussi l'appel à l'irrigation déficiente ainsi que la possibilité d’utilisation des eaux salées pour l’irrigation sont parmi les décisions à instaurer en Tunisie pour préserver le capital eau qui se fait de plus en plus rare.Méthodologie et résultats : Ces techniques d'irrigation ont été appliquées sur une culture de mil afin de tester sa tolérance au manque d’eau et à la salinité via sa variabilité génétique. Ainsi, trois écotypes de mil ont été cultivés selon un dispositif en split plot permettant de donner à l’eau d’irrigation la dose et la concentration en sel souhaitées. Les cinq traitements hydriques sont : deux doses d'irrigation déficientes, deux doses de sel et un témoin. A la maturité, les feuilles drapeaux sont collectées et la nutrition minérale a été déterminée. Lés résultats ont montré que le mil s'est comporté comme une espèce de type exclusif face aux contraintes hydriques et salines et que l'exclusion de Na+ est plus importante en milieu salin. Ce comportement caractérise les espèces tolérantes qui peuvent de plus, développer des mécanismes spécifiques pour limiter l’accumulation de Na+ dans leur tissu. L’étude écophysiologique des trois écotypes de mil a révélé qu'ils ont des comportements différents vis-à-vis du sel et de la sécheresse. Ils diffèrent aussi par la diversité des moyens qu’ils utilisent pour préserver leur intégrité et pour se défendre contre les agressions extérieures.Conclusion et application : De telles spécificités peuvent être exploitées pour répondre à des impératifs agronomiques intéressants et jouer un rôle dans la conservation et la mise en valeur des sols fragiles (phytoremédiation, pâturage)Mots clés : Mil- Sécheresse- Salinité- Osmolyte- Na+- K+

Seedling characters at different temperatures in pearl millet (Pennisetum glaucum (L.) R. Br.)

The effect of six temperatures ranging from 20 to 45°C on the germination and seedling length of six grain pearl millet genotypes (KS, AM, HG, EC, ZZ and D) was determined. There was significant variation in germination and seedling length across temperatures and among genotypes. As a result, significant temperature × genotype interactions occurred. Emergence problems, due to poor germination and inadequate seedling length, were likely found in certain genotypes at high and low seed temperature. The optimum temperature for coleoptile and radicle elongation was 30°C.Key words: Germination, pearl millet, temperature, seedling length, root length, genotype, coleoptile, Tunisia

Response of Tunisian autochthonous pearl millet (Pennisetum glaucum (L.) R. Br.) to drought stress induced by polyethylene glycol (PEG) 6000

Seeds of pearl millet (Pennisetum glaucum (L) R. Br.) from six provenances of Tunisia were subjected to germination and shoot and root length tests on filter paper treated with polyethylene glycol 6000 (PEG 6000) solutions made up to provide osmotic potentials of 0, -1 and -2 MPa. Mean germination percent for all provenances decreased about 73% in -2 MPa compared to control (0 MPa) treatment. Osmotic potential of -1.0 MPa improves the rate of germination but not significantly compared to the control. There were significant differences among the relative germination percent of the provenances in different treatments. Decreases in the external osmotic potential induced decreased shoot growth while a slight increase in root length associate with the -1 MPa treatments was observed for some ecotypes. This reflects an adaptive response involving an increase in root length to reach deeper water in the soil. It was also notified that the elongation of the radicle is more sensitive to the osmoticconstraint than the coleoptile

Pearl millet populations characterized by Fusarium prevalence, morphological traits, phenolic content, and antioxidant potential

Background: Pearl millet (Pennisetum glaucum L.) has become increasingly attractive due to its health benefits. It is grown as food for human consumption and fodder for livestock in Africa and Asia. This study focused on five pearl millet populations from different agro-ecological zones from Tunisia, and on characterization by morphological traits, total phenolic and flavonoid content, antioxidant activity, and occurrence of Fusarium. Results: Analysis of variance revealed highly significant differences between populations for the quantitative traits. The highest grain weights occurred in the pearlmillet cultivated in Zaafrana and Gergis of Tunisia. Early flowering and earlymaturing populations cultivated in the center (Zaafrana, Rejiche) and south (Gergis) of Tunisia tended to have a higher grain yield. The Zaafrana population showed the highest value of green fodder potentiel (number andweight of leaves/cultivar and theweight of tillers and total plant/cultivar) followed by Gergis and Rejiche. The Kelibia population showed the highest total phenolic and flavonoid content. Rejiche exhibited the greatest antioxidant activity. Trans-cinnamic, protocatechuic, and hydroxybenzoic acids were the major phenolic compounds in all the extracts. Three Fusarium species were identified in Tunisian pearl millet populations based on morphologic and molecular characterization. Fusarium graminearum and Fusarium culmorum occurred most frequently. The average incidence of the three Fusarium species was relatively low (<5%) in all populations. The lowest infection rate (0.1%) was recorded in the samples from Zaafrana. Conclusion: Chemometric analysis confirmed the usefulness of the above traits for discrimination of pearl millet populations, where a considerable variation according to geographical origin and bioclimatic conditions was observed. © 2020 Society of Chemical Industr

Evaluation and optimization of a commercial enzyme linked immunosorbent assay for detection of Chlamydophila pneumoniae IgA antibodies

<p>Abstract</p> <p>Background</p> <p>Serologic diagnosis of <it>Chlamydophila pneumoniae </it>(Cpn) infection routinely involves assays for the presence of IgG and IgM antibodies to Cpn. Although IgA antibodies to Cpn have been found to be of interest in the diagnosis of chronic infections, their significance in serological diagnosis remains unclear. The microimmunofluorescence (MIF) test is the current method for the measurement of Cpn antibodies. While commercial enzyme linked immunosorbent assays (ELISA) have been developed, they have not been fully validated. We therefore evaluated and optimized a commercial ELISA kit, the SeroCP IgA test, for the detection of Cpn IgA antibodies.</p> <p>Methods</p> <p>Serum samples from 94 patients with anti-Cpn IgG titers ≥ 256 (study group) and from 100 healthy blood donors (control group) were tested for the presence of IgA antibodies to Cpn, using our in-house MIF test and the SeroCP IgA test. Two graph receiver operating characteristic (TG-ROC) curves were created to optimize the cut off given by the manufacturer.</p> <p>Results</p> <p>The MIF and SeroCP IgA tests detected Cpn IgA antibodies in 72% and 89%, respectively, of sera from the study group, and in 9% and 35%, respectively, of sera from the control group. Using the MIF test as the reference method and the cut-off value of the ELISA test specified by the manufacturer for seropositivity and negativity, the two tests correlated in 76% of the samples, with an agreement of Ƙ = 0.54. When we applied the optimized cut-off value using TG-ROC analysis, 1.65, we observed better concordance (86%) and agreement (0.72) between the MIF and SeroCP IgA tests.</p> <p>Conclusion</p> <p>Use of TG-ROC analysis may help standardize and optimize ELISAs, which are simpler, more objective and less time consuming than the MIF test. Standardization and optimization of commercial ELISA kits may result in better performance.</p

Glycine Inhibitory Dysfunction Turns Touch into Pain through PKCgamma Interneurons

Dynamic mechanical allodynia is a widespread and intractable symptom of neuropathic pain for which there is a lack of effective therapy. During tactile allodynia, activation of the sensory fibers which normally detect touch elicits pain. Here we provide a new behavioral investigation into the dynamic component of tactile allodynia that developed in rats after segmental removal of glycine inhibition. Using in vivo electrophysiological recordings, we show that in this condition innocuous mechanical stimuli could activate superficial dorsal horn nociceptive specific neurons. These neurons do not normally respond to touch. We anatomically show that the activation was mediated through a local circuit involving neurons expressing the gamma isoform of protein kinase C (PKCγ). Selective inhibition of PKCγ as well as selective blockade of glutamate NMDA receptors in the superficial dorsal horn prevented both activation of the circuit and allodynia. Thus, our data demonstrates that a normally inactive circuit in the dorsal horn can be recruited to convert touch into pain. It also provides evidence that glycine inhibitory dysfunction gates tactile input to nociceptive specific neurons through PKCγ-dependent activation of a local, excitatory, NMDA receptor-dependent, circuit. As a consequence of these findings, we suggest that pharmacological inhibition of PKCγ might provide a new tool for alleviating allodynia in the clinical setting

Effets d'un stress hydrique appliqué à différents stades de développement sur l'aspect quantitatif et qualitatif des semences chez un écotype autochtone de sorgho grain (Sorghum bicolor)

Objectif : Les effets d'un stress hydrique appliqué à différents stades de développement sur l'aspect quantitatif et qualitatif des semences ont été étudiés chez un écotype autochtone de sorgho grain.Méthodologie et résultats : L’essai a été conduit en pots de végétation. L'irrigation des plantes a été faite par pesées successives des pots. Au cours de chaque pesée, le témoin est ramené au même poids correspondant à 70% de la réserve en eau utile ; alors que le traitement stressé (SI, S2 et S3) maintient le contenu en eau à 30 % de la RUE pendant 10 jours. A la fin du cycle de manque d'eau, l'irrigation a été reprise comme pour le témoin. Les stades concernés par le stress hydrique sont la phase d’initiation florale (S1), la phase de gonflement-épiaison (S2) et la phase de floraison - remplissage des grains (S3). Les résultats ont montré que le rendement et la qualité des semences baissent significativement lorsque le stress est appliqué au stade S2 et que le taux de germination et la vigueur des plantules (issues de S2) baissent en conséquence.Conclusion et application : de tels résultats amènent à affirmer que la phase phénologique la plus sensible au stress hydrique est celle du gonflement-épiaison. L'importance de cette étude trouve son application dans la gouvernance de l'irrigation. En effet, dans des conditions de pénurie d'eau, il faut mettre en place des scénarii permettant de livrer l'eau aux plantes seulement aux stades critiques de leur croissance afin d'éviter tout gaspillage.Mots clés : Sorgho, Écotype autochtone, Stress hydrique, Phase de développement, Rendement en grain

Glycine Inhibitory Dysfunction Turns Touch into Pain through PKCgamma Interneurons

International audienceDynamic mechanical allodynia is a widespread and intractable symptom of neuropathic pain for which there is a lack of effective therapy. During tactile allodynia, activation of the sensory fibers which normally detect touch elicits pain. Here we provide a new behavioral investigation into the dynamic component of tactile allodynia that developed in rats after segmental removal of glycine inhibition. Using in vivo electrophysiological recordings, we show that in this condition innocuous mechanical stimuli could activate superficial dorsal horn nociceptive specific neurons. These neurons do not normally respond to touch. We anatomically show that the activation was mediated through a local circuit involving neurons expressing the gamma isoform of protein kinase C (PKCc). Selective inhibition of PKCc as well as selective blockade of glutamate NMDA receptors in the superficial dorsal horn prevented both activation of the circuit and allodynia. Thus, our data demonstrates that a normally inactive circuit in the dorsal horn can be recruited to convert touch into pain. It also provides evidence that glycine inhibitory dysfunction gates tactile input to nociceptive specific neurons through PKCc-dependent activation of a local, excitatory, NMDA receptor-dependent, circuit. As a consequence of these findings, we suggest that pharmacological inhibition of PKCc might provide a new tool for alleviating allodynia in the clinical setting

Morphological and biochemical changes in maize under drought and salinity stresses in a semi-arid environment

This study investigated some morphological and biochemical responses of maize to drought and salinity in open field in Tunisia with the aim of gaining insights into tolerance mechanisms. After seedling emergence, five treatments were applied until maturity: optimal water supply (control, 100% of maximum evapotranspiration - ETM); irrigation at 70% ETM (moderate drought) and at 35% ETM (severe drought); optimal supply of water containing 3 g NaCl L 121 (moderate salinity) and 6 g NaCl L 121 (severe salinity). Here, we demonstrated that extreme drought and salinity severely decreased the leaf area ( 1274% and 1255%, respectively) and the above-ground biomass ( 1235% and 1231%, respectively) at silking stage, indicating that the photosynthetic leaf apparatus is highly sensitive and that drought has a greater effect than salinity. Grain yield losses were also exacerbated under extreme stress conditions, viz. severe drought ( 1285% versus controls) and severe salinity ( 1273%), while productivity under moderate salinity approximated that of moderate drought, possibly due to increases in leaf chlorophyll and carotenoid content and K/Na ratio. The leaf area and its relative water content were positively correlated with grain yield under both salinity and drought stresses, and may therefore be used as markers for effective screening of maize genotypes for better stress tolerance

Glycine inhibitory dysfunction turns touch into pain through astrocyte-derived D-serine

International audienceGlycine inhibitory dysfunction provides a useful experimental model for studying the mechanism of dynamic mechanical allodynia, a widespread and intractable symptom of neuropathic pain. In this model, allodynia expression relies on N-methyl-D-aspartate receptors (NMDARs), and it has been shown that astrocytes can regulate their activation through the release of the NMDAR coagonist D-serine. Recent studies also suggest that astrocytes potentially contribute to neuropathic pain. However, the involvement of astrocytes in dynamic mechanical allodynia remains unknown. Here, we show that after blockade of glycine inhibition, orofacial tactile stimuli activated medullary dorsal horn (MDH) astrocytes, but not microglia. Accordingly, the glia inhibitor fluorocitrate, but not the microglia inhibitor minocycline, prevented allodynia. Fluorocitrate also impeded activation of astrocytes and blocked activation of the superficial MDH neural circuit underlying allodynia, as revealed by study of Fos expression. MDH astrocytes are thus required for allodynia. They may also produce D-serine because astrocytic processes were selectively immunolabeled for serine racemase, the D-serine synthesizing enzyme. Accordingly, selective degradation of D-serine with D-amino acid oxidase applied in vivo prevented allodynia and activation of the underlying neural circuit. Conversely, allodynia blockade by fluorocitrate was reversed by exogenous D-serine. These results suggest the following scenario: removal of glycine inhibition makes tactile stimuli able to activate astrocytes; activated astrocytes may provide D-serine to enable NMDAR activation and thus allodynia. Such a contribution of astrocytes to pathological pain fuels the emerging concept that astrocytes are critical players in pain signaling