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Arbuscular mycorrhizal (AM) symbiosis is the oldest and most widespread mutualistic association on Earth and involves plants and soil fungi belonging to Glomeromycotina. A complex molecular, cellular, and genetic developmental program enables partner recognition, fungal accommodation in plant tissues, and activation of symbiotic functions such as transfer of phosphorus in exchange for carbohydrates and lipids. AM fungi, as ancient obligate biotrophs, have evolved strategies to circumvent plant defense responses to guarantee an intimate and long-lasting mutualism. They are among those root-associated microorganisms able to boost plants' ability to cope with biotic stresses leading to mycorrhiza-induced resistance (MIR), which can be effective across diverse hosts and against different attackers. Here, we examine the molecular mechanisms underlying the modulation of plant immunity during colonization by AM fungi and at the onset and display of MIR against belowground and aboveground pests and pathogens. Understanding the MIR efficiency spectrum and its regulation is of great importance to optimizing the biotechnological application of these beneficial microbes for sustainable crop protection. [ABSTRACT FROM AUTHOR]

Simple Summary: Skeletal muscle releases numerous hormones into circulation that interact with other organs, such as the liver, bone or the brain. These hormones, termed myokines, mediate the effects of physical activity in health, aging and disease. Interleukin 6 was the first discovered myokine and is actively investigated due to its participation in inflammation, immunity and metabolism. However, there is little information regarding the mechanisms that induce its release from muscle cells, especially in humans. Our aim was to investigate whether changes in the concentration of calcium ions participate in the stimulated release of interleukin 6 in human muscle cells. Using muscle cultures, we have found that several proteins responsible for the calcium increase during stimulation induce the release of interleukin 6 from the muscle cells. This could help to unveil how interleukin 6 and other myokines are released in pathological conditions such as trauma, infections or cancer. The systemic effects of physical activity are mediated by the release of IL-6 and other myokines from contracting muscle. Although the release of IL-6 from muscle has been extensively studied, the information on the cellular mechanisms is fragmentary and scarce, especially regarding the role of Ca2+ signals. The aim of this study was to characterize the role of the main components of Ca2+ signals in human skeletal muscle cells during IL-6 secretion stimulated by the Ca2+ mobilizing agonist ATP. Primary cultures were prepared from surgical samples, fluorescence microscopy was used to evaluate the Ca2+ signals and the stimulated release of IL-6 into the medium was determined using ELISA. Intracellular calcium chelator Bapta, low extracellular calcium and the Ca2+ channels blocker La3+ reduced the ATP-stimulated, but not the basal secretion. Secretion was inhibited by blockers of L-type (nifedipine, verapamil), T-type (NNC55-0396) and Orai1 (Synta66) Ca2+ channels and by silencing Orai1 expression. The same effect was achieved with inhibitors of ryanodine receptors (ryanodine, dantrolene) and IP3 receptors (xestospongin C, 2-APB, caffeine). Inhibitors of calmodulin (calmidazolium) and calcineurin (FK506) also decreased secretion. IL-6 transcription in response to ATP was not affected by Bapta or by the T channel blocker. Our results prove that ATP-stimulated IL-6 secretion is mediated at the post-transcriptional level by Ca2+ signals, including the mobilization of calcium stores, the activation of store-operated Ca2+ entry, and the subsequent activation of voltage-operated Ca2+ channels and calmodulin/calcineurin pathways. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal (AM) symbiosis is a beneficial symbiosis established between fungi of the phylum Glomeromycota and over 80% of terrestrial plants, including most agricultural and horticultural crop species. AM symbiosis improves the nutritional status and fitness of the host plant and enables the plant to perform better under stressful conditions. As a result, when plants are growing under unfavourable conditions, they try to recruit their AM fungal partner in the soil. Symbiosis establishment requires a complex chemical dialogue between the two partners, in which signalling molecules such as the strigolactones play a key role. Under deficient nutrient conditions, the host plant increases the production of strigolactones to promote fungal development and symbiosis establishment (a 'cry for help'). As a clue to host presence in the rhizosphere, strigolactones are also detected by other organisms, particularly root parasitic plants, and therefore promote a parasitic interaction. We review here the role of strigolactones and their interaction with other phytohormones during AM symbiosis, paying special attention to the implications of the chemical communication that takes place in the rhizosphere. Finally, we point out the potential use of this molecular dialogue as a target for developing new biological control strategies against deleterious organisms such as root parasitic weeds. Key words: strigolactones, rhizosphere communication, arbuscular mycorrhizal fungi, phytohormones, root parasitic plants, biological control. Les mycorhizes arbusculaires constituent (MA) une symbiose benefique etablie entre des champignons du phylum Glomeromycota et plus de 80 % des plantes terrestres, incluant la plupart des especes de plantes agricoles et horticoles. La symbiose MA ameliore le statut nutritif et l'adaptation de la plante hote et lui permet de mieux performer sous des conditions stressantes. C'est pourquoi, lorsque la plante pousse sous des conditions peu favorables, elle tente de recruter le champignon MA partenaire dans le sol. La mise en place de la symbiose necessite un dialogue chimique complexe entre les deux partenaires, au cours duquel des molecules de signalisation comme les strigolactones jouent un role determinant. Sous des conditions de nutrition deficientes, la plante hote augmente sa production de strigolactones pour stimuler le developpement du champignon et la mise en place de la symbiose (<< un appel a l'aide >>). Comme indication de la presence de la plante dans la rhizosphere, d' autres organismes peuvent aussi detecter les strigolacctones, surtout les plantes parasites des racines et ainsi etablir une interaction parasitaire accrue avec la plante. Les auteurs revisent le role des strigolactones et leurs interactions avec d'autres phytohormones au cours de la symbiose MA, en apportant une attention speciale a l'implication de la communication chimique qui prevaut dans la rhizosphere. Finalement, ils soulignent le potentiel de l'utilisation de ce dialogue, comme cible pour developper de nouvelles strategies de lutte biologique contre les organismes deleteres comme les plantes parasites des racines. Mots-cles : strigolactones, communication dans la rhizosphere, champignons mycorhiziens arbusculaires, phytohormones, plantes parasites des racines, lutte biologique. [Traduit par la Redaction], Introduction Plants are living organisms that continuously and reciprocally communicate with other organisms in their environment. This communication relies on chemicals as signalling molecules to perceive environmental changes. Plants use [...]

Populations of interstitial cells of Cajal (ICC) are altered in several gastrointestinal neuromuscular disorders. ICC are identified typically by ultrastructure and expression of Kit (CDll7), a protein that is also expressed on mast cells. No other molecular marker currently exists to independently identify ICC. The expression of ANO1 (DOG1, TMEMI6A), a [Ca.sup.2+]-activated [Cl.sup.-] channel, in gastrointestinal stromal tumors suggests it may be useful as an ICC marker. The aims of this study were therefore to determine the distribution of Anol immunoreactivity compared with Kit and to establish whether Anol is a reliable marker for human and mouse ICC. Expression of Anol in human and mouse stomach, small intestine, and colon was investigated by immunofluorescence labeling using antibodies to Anol alone and in combination with antibodies to Kit. Colocalization of immunoreactivity was demonstrated by epifluorescence and confocal microscopy. In the muscularis propria, Anol immunoreactivity was restricted to cells with the morphology and distribution of ICC. All Ano 1-positive cells in the muscularis propria were also Kit positive. Kit-expressing mast cells were not Anol positive. Some non-ICC in the mucosa and submucosa of human tissues were Anol positive but Kit negative. A few (3.2%) Anol-positive cells in the human gastric muscularis propria were labeled weakly for Kit. Anol labels all classes of ICC and represents a highly specific marker for studying the distribution of ICC in mouse and human tissues with an advantage over Kit since it does not label mast cells. Kit; mast cells; chloride channels; gastrointestinal motility; immunofluorescence

Relatively little is known about the contribution of [Ca.sup.2+]-dependent and -independent mechanisms in the contractility of neonatal gastrointestinal smooth muscle. We therefore studied [Ca.sup.2+] homeostasis and [Ca.sup.2+] sensitization mechanisms in 10-day-old and adult guinea pig gallbladder smooth muscle to elucidate developmental changes in these processes. Gallbladder contractility was evaluated by isometrical tension recordings from strips, intracellular [Ca.sup.2+] concentration was estimated by epifluorescence microscopy of fura-2-loaded isolated cells, and protein expression and phosphorylation were assessed by Western blot analysis. The neonatal gallbladder contracted significantly less to CCK than adult tissue, but this correlated with an increased [Ca.sup.2+] mobilization, suggesting immaturity of [Ca.sup.2+] sensitization mechanisms. The enhanced [Ca.sup.2+] release in the newborn gallbladder was the result of the increase in the size of the releasable [Ca.sup.2+] pool. Moreover, in neonatal smooth muscle cells, neither the plasma membrane [Ca.sup.2+] pump nor the [Na.sup.+]/[Ca.sup.2+] exchanger collaborate in the extrusion of [Ca.sup.2+]. In contrast, in these cells, there is an increase in phospholamban phosphorylation, which could drive to an overactivity of the sarco(endo)plasmic reticulum [Ca.sup.2+]-ATPase pump. The reduced [Ca.sup.2+] sensitivity in neonatal tissues was demonstrated by the lack of effect to Y-27362, an inhibitor of Rho kinase (ROCK), and GF-109203X, an inhibitor of PKC, on agonist-induced contraction. In addition, the neonatal gallbladder showed lower levels of RhoA, ROCK, PKC, and two effectors [C-kinase-dependent inhibitor of 17 kDa (CPI-17) and myosin phosphatase targetting 1 (MYPT1)] as well as an absence of CPI-17 and MYPT1 phosphorylation in response to agonists. In conclusion, our results indicate that the main mechanisms involved in smooth muscle contractility are under developmental regulation. [Ca.sup.2+]-dependent contraction; [Ca.sup.2+] sensitization; gastrointestinal smooth muscle