Salicylic acid is a phenolic phytohormone which controls plant growth and development. A methyl ester (MSA) derivative thereof is volatile and involved in plant-insect or plant-plant communication. Here we show that the nematode-trapping fungus Duddingtonia flagrans uses a methyl-salicylic acid isomer, 6-MSA as morphogen for spatiotemporal control of trap formation and as chemoattractant to lure Caenorhabditis elegans into fungal colonies. 6-MSA is the product of a polyketide synthase and an intermediate in the biosynthesis of arthrosporols. The polyketide synthase (ArtA), produces 6-MSA in hyphal tips, and is uncoupled from other enzymes required for the conversion of 6-MSA to arthrosporols, which are produced in older hyphae. 6-MSA and arthrosporols both block trap formation. The presence of nematodes inhibits 6-MSA and arthrosporol biosyntheses and thereby enables trap formation. 6-MSA and arthrosporols are thus morphogens with some functions similar to quorum-sensing molecules. We show that 6-MSA is important in interkingdom communication between fungi and nematodes.

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The paper is focused on the behavior of deep beams retrofitted with FRP sheets and layers In order to understand the behavior of these beams, and an advanced nonlinear finite element model is used. The nonlinear analyses were performed based on the Modified Compression Field Theory which is a smeared rotating crack approach implemented in program VecTor2. The predictions of the finite element models were compared to the test results in order to validate the models and to further understand the behavior of the test specimens. Finally, the validated model was used to perform parametrical studies to investigate the effect of FRP sheets and UHPFRC layers on the behavior of true-scale deep beams. The variables investigated in a systematic manner included the aspect ratio of the member, the layout of the FRP sheets, the thickness and fiber content of the UHPFRC layers. The results were used to compare the effectiveness of the two retrofitting techniques.

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