Mechanical forces exerted on floral primordia with a novel experimental system modify floral development in Arabidopsis thaliana.

Mechanical forces play a crucial role in plant development, including floral development. We previously reported that the phyllotactic variation in the staminate flowers of Ceratophyllum demersum may be caused by mechanical forces on the adaxial side of floral primordia, which may be a common mechanism in angiosperms. On the basis of this result, we developed a novel experimental system for analysis of the effects of mechanical forces on the floral meristem of Arabidopsis thaliana, aiming to induce morphological changes in flowers. In this experimental system, a micromanipulator equipped with a micro device, which is shaped to conform with the contour of the abaxial side of the young floral primordium, is used to exert contact pressure on a floral primordium. In the present study, we conducted contact experiments using this system and successfully induced diverse morphological changes during floral primordial development. In several primordia, the tip of the abaxial sepal primordium was incised with two or three lobes. A different floral primordium developed an additional sepal on the abaxial side (i.e., two abaxial sepals). Additionally, we observed the fusion of sepals in some floral primordia. These results suggest that mechanical forces have multiple effects on floral development, and changes in the tensile stress pattern in the cells of floral primordia are induced by the mechanical forces exerted with the micro device. These effects, in turn, lead to morphological changes in the floral primordia.

Lactose hydrate can increase the transcellular permeability of ß-naphthol in rat jejunum and ileum.

BACKGROUND: The unstirred water layer (UWL) is an integral part of the apical surface of mucosal epithelia and comprises mucins (MUC), for which there are many molecular species. Galectins, a family of ß-galactoside-binding lectins, form a lattice barrier on surface epithelial cells by interacting with MUC. Lactose inhibits the galectin-MUC interaction. Therefore, the present study investigated the galectin-MUC interaction in the mucosa of the gastrointestinal tract and its role in intestinal barrier functions. MATERIALS AND RESULTS: The effects of lactose hydrate (LH) on the membrane permeability of the rat small intestine and Caco-2 cells were examined. LH enhanced the membrane permeability of the rat small intestine, which contains the UWL, via a transcellular route, for which the UWL is the rate limiting factor. The membrane permeability of Caco-2 cells, in which the UWL is insufficient, was not affected by LH. The apparent permeability coefficient (Papp) of a paracellular marker was not significantly altered in the rat small intestine or Caco-2 cells treated with LH at any concentration. Furthermore, the Papp of ß-naphthol which is a transcellular marker was not significantly altered in Caco-2 cells treated with LH, but was significantly increased in the rat small intestine in a LH concentration-dependent manner. CONCLUSIONS: The present results demonstrate that the physical barrier has an important function in gastrointestinal membrane permeability, and LH-induced changes increase the transcellular permeability of ß-naphthol in rat small intestine.