(with detailed structure of adhesive organs. nontoxic and tissue-compatible, and are able to function ABT-888 (Veliparib) under wet conditions. However, little is known about the mechanisms underlying biological adhesives. We characterized adhesion and release in our model system features a duo-gland adhesive system that allows it to repeatedly attach to and release from substrates in seawater within a minute. However, little is known about the molecules involved in this temporary adhesion. In this Foxo1 study, we show that this attachment of relies on the secretion of two large adhesive proteins, adhesion protein 1 (Mlig-ap1) and Mlig-ap2. We revealed that both proteins are expressed in the adhesive gland cells and that their distribution within the adhesive footprints was spatially restricted. RNA interference knockdown experiments exhibited the essential function of these two proteins in flatworm adhesion. Negatively charged modified sugars ABT-888 (Veliparib) in the surrounding water inhibited flatworm attachment, while positively charged molecules impeded detachment. In addition, we found that could not adhere to strongly hydrated surfaces. We propose an attachmentCrelease model where Mlig-ap2 attaches to the substrate and Mlig-ap1 exhibits a cohesive function. A small negatively charged molecule is usually secreted that interferes with Mlig-ap1, inducing detachment. These findings are of relevance for fundamental adhesion science and efforts to mitigate biofouling. Further, this model of flatworm temporary adhesion may serve as the starting point for the development of synthetic reversible adhesion systems for medicinal and ABT-888 (Veliparib) industrial applications. Bioadhesion is the attachment of an organism to a surface using natural macromolecules. An increasing number of studies have focused on the investigation of marine biological adhesives and the development of biomimetic counterparts (1C3). Bioadhesives could be a nontoxic, biodegradable, and yet strong-adhering alternative to the medical adhesives currently in use (4). Biological attachment is usually a common feature among several marine invertebrate species (5). It is essential for feeding, locomotion, defense, mating, and to prevent dislodgement (6). Bioadhesion can be divided into permanent and temporary attachment systems (7). To date, most scientific advances have been made in the characterization of permanent adhesives, such as those of mussels, tubeworms, and barnacles (8C10). In contrast to permanent adhesion, animals with temporary adhesive systems can voluntarily detach ABT-888 (Veliparib) from a substrate. After detachment, the secreted adhesive material stays permanently attached to the surface as so-called footprints. Such systems are found in echinoderms (7, 11) and flatworms (12C14). To date, reversible adhesion and its related secretions are poorly comprehended, and only certain components have been identified (15C18). Free-living marine and freshwater Platyhelminthes use a duo-gland adhesive system to adhere and release (13, 19). Their adhesive system consists of dozens to hundreds of adhesive organs. Each adhesive organ comprises three cell types: the adhesive gland, a releasing gland, and a modified epidermal cell, called an anchor cell (13, 14). However, little is known about the composition of the adhesive substances. Our model system, can attach and release several times to any substrate within a single minute (12, 20). A broad molecular toolbox for has been established, including whole-mount in situ hybridization, RNA interference (RNAi), and transgenesis (20C33), allowing adhesion studies not feasible in other adhering species. In this study, we present a characterization of the adhesive substances used for temporary adhesion in a flatworm species. We identified two large adhesion proteins and analyzed their secretion upon attachment. Both proteins showed particular characteristics, such as high cysteine content, large repetitive regions, and a number of known proteinCcarbohydrate and proteinCprotein conversation domains. The essential function of the proteins in the adhesion process was corroborated with RNAi-mediated knockdown. We performed attachment assays and tested different molecules and surfaces regarding their interference with attachment and release. In addition, we showed that negatively charged sugars were able to inhibit the adhesion, while positively charged molecules interfered with the natural detachment of the flatworm. These results were incorporated into a model for the attachment and release of adhesion protein 1 (Mlig-ap1) and Mlig-ap2, comprising 5,407 and 14,794 amino acids, respectively. and transcripts were expressed in cells located in the flatworm tail (Fig. 1 adhesive proteins. (with detailed structure of adhesive organs. (and mRNA visualized with colorimetric WISH (and (22, 24) revealed that multiple impartial transcripts of the MLRNA815 transcriptome (21) were expressed in the tail (22, 24). Based on.