Aquaporins in developing rice grains

During rice grain filling, grain moisture content and weight show dynamic changes. We focused on the expression of all 33 rice aquaporins in developing grains. Only two aquaporin genes, OsPIP2;1 and OsTIP3;1, were highly expressed in the period 10–25 days after heading (DAH). High-temperature treatment from 7 to 21 DAH abolished the dynamic up-regulation of OsPIP2;1 in the period 15–20 DAH, whereas OsTIP3;1 expression was not affected. Immunohistochemical analysis revealed that OsPIP2;1 was present in the starchy endosperm, nucellar projection, nucellar epidermis, and dorsal vascular bundles, but not in the aleurone layer. OsTIP3;1 was present in the aleurone layer and starchy endosperm. Water transport activity of recombinant OsTIP3;1 was low, in contrast to the high activity of recombinant OsPIP2;1 we reported previously. Our data suggest that OsPIP2;1 and OsTIP3;1 have distinct roles in developing grains.     

Environmental factors determining the distribution of highland plants at low-altitude algific talus sites

Algific talus is a micro-scale habitat type where highland plants (subalpine and alpine species) are found, disjunct from their typical range, in lowland forests. On algific talus, cold airflows from the interstices between talus fragments create a local microclimate colder than surrounding forests. Despite of the widely-known occurrence of unique vegetation on algific talus, critical environmental factors determining the distribution of highland species in this habitat type are unclear. In order to reveal the environmental factors enabling highland species to inhabit algific talus, we investigated the vegetation and environments of 26 algific talus sites and four reference (non-algific talus) sites in Hokkaido, northern Japan. Several algific talus sites were dominated by highland species, while some algific talus sites and all non-algific talus sites were dominated by lowland species. Community analysis based on detrended correspondence analysis (DCA) and canonical corresponding analysis (CCA) revealed that the algific talus sites dominated by highland species had lower ground temperature, more acidic soil, larger canopy openness, and less diverse vegetation than the sites dominated by lowland species. Highland plants might be maintained under conditions stressful for lowland plants, resulting in less competitive situation. Generalized linear models (GLM), used to evaluate the response of individual highland species to environmental factors, revealed that preferable environmental conditions for highland plants are highly species specific. These results indicate that the maintenance of diverse environments is crucial for the conservation of the unique vegetation and local populations of highland species in algific talus areas.     

Crucial role of the small GTPase ARF6 in hepatic cord formation during liver development

The mammalian small GTPase ADP-ribosylation factor 6 (ARF6) plays important roles in a wide variety of cellular events, including endocytosis, actin cytoskeletal reorganization, and phosphoinositide metabolism. However, physiological functions for ARF6 have not previously been examined. Here, we described the consequence of ARF6 ablation in mice, which manifests most obviously in the context of liver development. Livers from ARF6-/- embryos are smaller and exhibit hypocellularity, due to the onset of midgestational liver cell apoptosis. Preceding the apoptosis, however, defective hepatic cord formation is observed; the liver cells migrate abnormally upon exiting the primordial hepatic epithelial sheet and clump rather than becoming dispersed. Consistent with this observation, the ability of hepatocyte growth factor/scatter factor (HGF) to induce hepatic cord-like structures from ARF6-/- fetal hepatocytes cultured in vitro in collagen gel matrix is impaired. Finally, we show that endogenous ARF6 in wild-type fetal hepatocytes is activated in response to HGF stimulation. These results provide evidence that ARF6 is an essential component in the signaling pathway coupling HGF signaling to hepatic cord formation.     

Persistent Release of IL-1s from Skin Is Associated with Systemic Cardio-Vascular Disease,Emaciation and Systemic Amyloidosis: The Potential of Anti-IL-1 Therapy for Systemic Inflammatory Diseases

The skin is an immune organ that contains innate and acquired immune systems and thus is able to respond to exogenous stimuli producing large amount of proinflammatory cytokines including IL-1 and IL-1 family members. The role of the epidermal IL-1 is not limited to initiation of local inflammatory responses, but also to induction of systemic inflammation. However, association of persistent release of IL-1 family members from severe skin inflammatory diseases such as psoriasis, epidermolysis bullosa, atopic dermatitis, blistering diseases and desmoglein-1 deficiency syndrome with diseases in systemic organs have not been so far assessed. Here, we showed the occurrence of severe systemic cardiovascular diseases and metabolic abnormalities including aberrant vascular wall remodeling with aortic stenosis, cardiomegaly, impaired limb and tail circulation, fatty tissue loss and systemic amyloid deposition in multiple organs with liver and kidney dysfunction in mouse models with severe dermatitis caused by persistent release of IL-1s from the skin. These morbid conditions were ameliorated by simultaneous administration of anti-IL-1α and IL-1β antibodies. These findings may explain the morbid association of arteriosclerosis, heart involvement, amyloidosis and cachexia in severe systemic skin diseases and systemic autoinflammatory diseases, and support the value of anti-IL-1 therapy for systemic inflammatory diseases.     

Strigolactone Positively Controls Crown Root Elongation in Rice

Strigolactones are recently identified plant hormones that inhibit shoot branching. Pleiotropic defects in strigolactone-deficient or -insensitive mutants indicate that strigolactones control various aspects of plant growth and development. However, our understanding of the hormonal function of strigolactones in plants is very limited. In this study we demonstrate that rice dwarf mutants that are strigolactone-deficient or -insensitive exhibit a short crown root phenotype. Exogenous application of GR24, a synthetic strigolactone analog, complemented the crown root defect in strigolactone-deficient mutants but not in strigolactone-insensitive mutants. These observations imply that strigolactones positively regulate the length of crown roots. Histological observations revealed that the meristematic zone is shorter in dwarf mutants than in wild type, suggesting that strigolactones may exert their effect on roots via the control of cell division. We also show that crown roots of wild type, but not dwarf mutants, become longer under phosphate starvation.