Regulatory expression of MDP77 protein in the skeletal and cardiac muscles

The mdp77 gene was first cloned from the cDNA library of denervated chick muscles, while its role(s) in vivo was unknown. In the present study, using specific polyclonal antibodies against MDP77, we show that MDP77 was expressed specifically in the skeletal and cardiac muscle, and confirm its presence in the cytoplasm of the extrafusal muscle fibers. In mature muscles, MDP77 immunoreactivity was observed in a repetitive manner along the sarcomere. The onset of MDP77 expression occurred just after myotube formation both in vivo and in vitro. Furthermore, MDP77 was enriched in the intrafusal muscle fibers. Our findings suggest that MDP77 plays an important role(s) in the differentiation, maturation and function of both the skeletal and cardiac muscles.     

Functional expression of Acetabularia acetabulum vacuolar H(+)-pyrophosphatase in a yeast VMA3-deficient strain

The function of the translation product of cDNA for Acetabularia vacuolar H(+)-pyrophosphatase was examined using the Saccharomyces cerevisiae VMA3-deficient strain. The open reading frame of Acetabularia H(+)-pyrophosphatase was revealed to encode 751 amino acids (721 or 751 amino acids in a previous paper). The acidification of the vacuole was observed by fluorescence microscopy when the cDNA was constructed in pYES2. Immunoblot analysis also supported the localization of the translation product in the vacuolar-membrane-enriched fraction.     

Importance of permafrost as a source of water for plants in east Siberian taiga

Stable oxygen isotope ratios of plant water (sap water) were observed at Spasskaya Pad experimental forest near Yakutsk, Russia in 1997–1999. The ¹⁸O of sap water in larch trees (Larix gmelinii) decreased soon after leaf unfolding every year, indicating that snowmelt water was used in the beginning of summer. During mid to late summer, a clear difference in the water source used by plants was observed between wet summers and severe drought summers. The ¹⁸O values of water in larch trees were high (–17.8 to –16.1) in August 1999 (wet summer), but low (–20.4 to –19.7) in August 1998 (drought summer). These results indicated that plants used rainwater during a wet summer, but meltwater from permafrost was used by plants during a drought summer. One important role of permafrost is to provide a direct source of water for plants in a severe drought summer; another role is to keep surplus water in the soil until the next summer. If this permafrost system is disturbed by future global warming, unique monotypic stands of deciduous larch trees in east Siberia might be seriously damaged in a severe drought summer.     

Cloning and characterization of a novel synaptosome-enriched mRNA that encodes 31 kDa protein

Although a subpopulation of mRNAs has been identified as translocated to the dendrites or the synaptic regions of neurons, the translocational mechanism has not been elucidated. To find mRNAs enriched in synapses, we compared the synaptosomal mRNAs with those from whole forebrain using differential display (DD). We cloned one of these mRNAs, which encoded a novel 31 kDa protein (PMES-2). PMES-2 mRNA was specifically transcribed in the brain and was present in the dendrites of the hippocampal neurons. PMES-2 protein was partly localized in the postsynaptic density. Although this protein is very similar to human NABC1 protein, its function is still unknown.     

Balancing the central roles of the thylakoid proton gradient

The photosynthetic electron transfer chain generates proton motive force (pmf), composed of both electric field (Deltapsi) and concentration (DeltapH) gradients. Both components can drive ATP synthesis, whereas the DeltapH component alone can trigger feedback regulation of the antenna. It has often been suggested that a relatively large pmf is needed to sustain the energetic contributions of the ATP synthase reaction (DeltaG(ATP)), and that the Deltapsi component is dissipated during illumination, leading to an acidic lumen in the light. We suggest that this is incompatible with the stabilities of lumenal components and the observed activation of downregulation. Recent work on the chloroplast ATP synthase suggests that a more moderate pmf can sustain DeltaG(ATP). In addition, in vivo probes suggest that a substantial fraction of pmf can be stored as Deltapsi. Together, these factors should allow sufficient DeltaG(ATP) to maintain lumen pH in a range where lumenal enzyme activities are nearly optimal, and where the level of NPQ is regulated.     

Significance of rooting depth in mire plants: Evidence from natural <Superscript>15</Superscript>N abundance

Variation in stable nitrogen isotope ratios (¹⁵N) was assessed for plants comprising two wetland communities, a bog-fen system and a flood plain, in central Japan. ¹⁵N of 12 species from the bog-fen system and six species from the flood plain were remarkably variable, ranging from –5.9 to +1.1 and from +3.1 to +8.7, respectively. Phragmites australis exhibited the highest ¹⁵N value at both sites. Rooting depth also differed greatly with plant species, ranging from 5cm to over 200cm in the bog-fen system. There was a tendency for plants having deeper root systems to exhibit higher ¹⁵N values; plant ¹⁵N was positively associated with rooting depth. Moreover, an increasing gradient of peat ¹⁵N was found along with depth. This evidence, together with the fact that inorganic nitrogen was depleted under a deep-rooted Phragmites australis stand, strongly suggests that deep-rooted plants actually absorb nitrogen from the deep peat layer. Thus, we successfully demonstrated the diverse traits of nitrogen nutrition among mire plants using stable isotope analysis. The ecological significance of deep rooting in mire plants is that it enables those plants to monopolize nutrients in deep substratum layers. This advantage should compensate for any consequential structural and/or physiological costs. Good evidence of the benefits of deep rooting is provided by the fact that Phragmites australis dominates as a tall mire grass.     

Diversity and rarity hotspots and conservation of butterfly communities in and around the Aokigahara woodland of Mount Fuji,central Japan

In central Japan, Aokigahara woodland is considered to be one of the most natural areas around Mount Fuji and a core area in the conservation of the biodiversity of Mount Fuji. We chose butterflies as an indicator species of biodiversity and examined six communities in and around the woodland in 2000 using transect counts to examine and search for diversity and rarity hotspots and their associated landscapes. The results showed that butterfly species richness and species diversities H 1/ were significantly higher in forest-edge sites than in forest-interior and/or open-land sites, and variation in the total number of species among these three landscape types was well accounted for by ecologically specialist species, such as landscape specifics, oligovoltines, narrow diet feeders and low-density species. Thus, the species regarded as vulnerable to extinction, including Red List species, were observed more often in forest-edge sites than in forest-interior and/or open-land sites. As a result, in the study area, diversity and rarity hotspots were found in forest-edge landscapes. The reasons why butterfly diversity and rarity hotspots were established in forest-edge landscapes were analyzed and interpreted from several points of view, including disturbance level, landscape elements and plant species richness. From these results, and the fact that some species were confined to forest-interior sites, we conclude that it is very important to conserve and manage forest-edge habitats (considered to be semi-natural) as well as forest-interior habitats (considered to be the most natural) to maintain the diversity of butterfly communities and preserve the various types of threatened species in and around the Aokigahara woodland.