Highlights d The mechanical properties of the chordotonal organ are altered in Pericardin mutants d Loss of Pericardin drives a transition from compression to bending in the cap cell d Compressive strain within the cap cell is essential for proper sensing d The results can be interpreted using a simplified model of an elastic beam

In the Drosophila larva, major proprioceptive input is provided to the brain by subepidermal stretch receptors called chordotonal organs (ChO). Similarly to the body wall muscle that needs to be attached on both of its sides to the larval exoskeleton in order to generate movement, the sensory unit of a ChO must be stably anchored to the cuticle on both of its sides in order to sense the relative displacement of body parts. Through an RNAi screen we have identified thrombospondin (Tsp), a secreted calcium binding glycoprotein, as a critical component in the anchoring of ChOs to the cuticle. We show that the Tsp protein starts to accumulate in the extracellular matrix (ECM) surrounding the ChO attachment cells towards the end of embryogenesis and that it becomes highly concentrated at the attachment junction during larval stages. In the absence of Tsp, the ChO's accessory cells fail to form a stable junction with their epidermal attachment cells and organ integrity is not maintained. Tsp is a known player in the establishment of the myotendinous junctions in both invertebrates and vertebrates. Thus, our findings extend the known similarities between muscle-attachment and ChO-attachment cells. In addition to its role in establishing the ChO attachment junctions, Tsp was found to affect ligament cell migration and cap cell elongation. Most interestingly, the Tsp protein was found to decorate the ChO cap cells along their entire length, suggesting that the elongated cap cells are supported by the ECM to which they attach via integrin-based, Tsp-dependent, adhesion plaques. The ECM enwrapping the cap cells is probably important for keeping the cap cells fasciculate and may also provide mechanical support that allows the extremely elongated cells to maintain tension.

Background Modulating the microbiota is a leading-edge strategy for the restoration and maintenance of a healthy, balanced environment. The use of health-promoting bacteria has demonstrated some potential benefits as an alternative for skin microbiota intervention. Here, we investigate the manipulation of mice skin microbiota using B. subtilis incorporated into a supportive Pluronic F-127 hydrogel formulation. The formula plays an important role in delivering the bacteria to the desired action site. Results The B. subtilis challenge induced a shift in the composition and abundance of the skin microbiota. Containment of B. subtilis in the Pluronic F-127 hydrogel accelerated bacterial modulation compared with free B. subtilis. The abundance of both Staphylococcus and Corynebacterium spp. was altered as a result of the live bacterial intervention: the abundance of Corynebacterium increased while that of Staphylococcus decreased. Four days after last application of the B. subtilis formulation, B. subtilis counts returned to its initial level. Conclusions B. subtilis intervention can induce a shift in the skin microbiota, influencing the abundance of commensal, beneficial, and pathogenic bacteria. Containment of B. subtilis in Pluronic hydrogel accelerates the microbial alteration, probably by facilitating bacterial attachment and supporting continuous growth. Our results reveal the ability of B. subtilis in Pluronic to modulate the skin microbiota composition, suggesting that the formulation holds therapeutic potential for skin disease treatment.

Background Modulating the microbiota is a leading-edge strategy for the restoration and maintenance of a healthy, balanced environment. The use of health-promoting bacteria is emerging as an alternative for skin microbiota intervention, showing promising results. Bacillus subtilis, with its non-pathogenic and antibacterial properties, has great potential as a microbiota-manipulating agent. Here, we investigate the experimental manipulation of the skin microbiota using B. subtilis incorporated into a supportive Pluronic F-127 hydrogel formulation. Indeed, the formulation is of prime importance for dermal bacterial delivery, determining the ability of live bacteria to become established at the desired action site. Results The B. subtilis challenge induced a shift in the composition and abundance of the skin microbiota. Containment of B. subtilis in the Pluronic F-127 hydrogel accelerated bacterial modulation compared with free B. subtilis. The abundance of both Staphylococcus and Corynebacterium spp. was altered as a result of the live bacterial intervention: the abundance of Corynebacterium increased while that of Staphylococcus decreased. Four days after last application of the B. subtilis formulation, B. subtilis counts returned to its initial level. Conclusions B. subtilis intervention can induce a shift in the skin microbiota, with an increased presence of commensal, benefit-associated bacteria and a reduced abundance of pathogen-containing bacterial genera. Containment of B. subtilis in Pluronic hydrogel accelerates the microbial alteration, probably by facilitating bacterial attachment and supporting continuous growth. Our results reveal the ability of B. subtilis in Pluronic to modulate the skin microbiota composition, suggesting that the formulation holds therapeutic potential for skin disease treatment.

SummaryThe organization of the root meristem is maintained by a complex interplay between plant hormones signaling pathways that both interpret and determine their accumulation and distribution. Brassinosteroids (BR) and auxin signaling pathways control the number of meristematic cells in the Arabidopsis root, via an interaction that appears to involve contradicting molecular outcomes, with BR promoting auxin signaling input but also repressing its output. However, whether this seemingly incoherent effect is significant for meristem function is unclear. Here, we established that a dual effect of BR on auxin, with BR simultaneously promoting auxin biosynthesis and repressing auxin transcriptional output, is essential for meristem maintenance. Blocking BR-induced auxin synthesis resulted in rapid BR-mediated meristem loss. Conversely, plants with reduced BR levels were resistant to loss of auxin biosynthesis and these meristems maintained their normal morphology despite a 10-fold decrease in auxin levels. In agreement, injured root meristems which rely solely on local auxin synthesis, regenerated when both auxin and BR synthesis were inhibited. Use of BIN2 as a tool to selectively inhibit BR signaling, revealed meristems with distinct phenotypes depending on the perturbed tissue; meristem reminiscent of BR-deficient mutants or of high BR exposure. This enabled mapping BR-auxin interactions to the outer epidermis and lateral root cap tissues, and demonstrated the essentiality of BR signaling in these tissues for meristem maintenance. BR activity in internal tissues however, proved necessary to control BR homeostasis. Together, we demonstrate a basis for inter-tissue coordination and how a critical ratio between these hormones determines the meristematic state.