Riboswitches are genetic control elements that regulate gene expression in a small molecule-dependent way. We developed a two-stage strategy of in vitro selection followed by a genetic screen and identified several artificial small molecule-binding riboswitches that respond to the aminoglycoside neomycin. Structure-function relationships and structural probing revealed that they adopt the general neomycin-binding motif. They display no sequence similarities to in vitro selected neomycin aptamers but contain parts of the decoding site that is the binding site for neomycin on the ribosomal RNA. We propose a model of a composed binding pocket of an internal loop as primary docking site and a terminal flaplike loop structure fixing neomycin in a sandwich-like manner. Such binding pockets characterized by multiple contacts between ligand and RNA are described for both natural and engineered riboswitches. We anticipate that combination of in vitro selection and in vivo screening is a useful strategy to identify RNA molecules with a desired functionality.

We present a study of the seasonal behaviour of soil moisture in an old embankment levee by means of 2D DC-electrical resistivity tomography monitoring based on an embedded electrode installation. We were able to produce seasonal resistivity change models that are compensated for temperature effects using a seasonal temperature profile model. Time-lapse sections of percentage resistivity changes show spatial and temporal overall consistency with seasonal variations of soil temperature. Discrepancies are likely due to the pavement layer that is not well considered in the inversion process as well as to time-lapse inversion pitfalls. Furthermore, a detailed estimation of seasonal moisture content variations could not be given as an accurate calibration of the employed suction probes was not achievable. Nevertheless, the levee appears to have spatially consistent time variations in soil moisture, clearly influenced by both rainfall and water table and river levels. Future work on developing 3D acquisitions and adding embedded moisture content probes should prove effective to our monitoring design and give a more detailed understanding of the soil moisture seasonal behaviour in the studied stretch of levee.

International audienc