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61.
Seagrasses are composed of four families belonging to angiosperms and they are thought to become adaptive to aquatic life independently. Zosteraceae is one such family and because of the relatively high species diversity around Japan and Korea coast areas, the family might have arisen therefrom. To elucidate the origin and evolution of Zosteraceae which consists of three genera, Phyllospadix, Zostera, and Heterozostera, 2.8 kb nucleotide sequences of rbcL and matK genes in the chloroplast genome were examined for various species, including cosmopolitan Z. marina and endemic Z. caulescens. The phylogenetic analysis reveals the following three features. First, based on the synonymous nucleotide substitution rate of the rice chloroplast genome, we estimated the divergence times between Zosteraceae and its closest relative, Potamogetonaceae, and between different genera, Zostera and Phyllospadix, as approximately 100 million years (myr) and 36 myr, respectively, suggesting that Zosteraceae emerged somewhere in the period from 36 myr ago to 100 myr ago. Second, two subgenera of Zostera, Zostera and Zosterella, exhibit their reciprocal monophyly and appear to have differentiated from each other approximately 33 myr ago. However, the third genus Heterozostera branched off only 5 myr ago from the stem lineage leading to Zosterella and this seems too recent in comparison with the ancient divergence of the two subgenera. Third, we estimated the most recent common ancestor of subgenus Zostera as 6 myr. In Z. marina four haplotypes were found in the sample and have diversified in the past 1.5 myr. One haplotype is shared by both sides of the Japan Archipelago and its closely related haplotypes occur also in eastern Pacific Ocean. Based on these phylogeographic analyses, we propose a provisional age related classification of Zosteraceae to argue the origin and evolution. 相似文献
62.
Yokomaku D Numakawa T Numakawa Y Suzuki S Matsumoto T Adachi N Nishio C Taguchi T Hatanaka H 《Molecular endocrinology (Baltimore, Md.)》2003,17(5):831-844
Changes in synaptic efficacy are considered necessary for learning and memory. Recently, it has been suggested that estrogen controls synaptic function in the central nervous system. However, it is unclear how estrogen regulates synaptic function in central nervous system neurons. We found that estrogen potentiated presynaptic function in cultured hippocampal neurons. Chronic treatment with estradiol (1 or 10 nm) for 24 h significantly increased a high potassium-induced glutamate release. The estrogen-potentiated glutamate release required the activation of both phosphatidylinositol 3-kinase and MAPK.The high potassium-evoked release with or without estradiol pretreatment was blocked by tetanus neurotoxin, which is an inhibitor of exocytosis. In addition, the reduction in intensity of FM1-43 fluorescence, which labeled presynaptic vesicles, was enhanced by estradiol, suggesting that estradiol potentiated the exocytotic mechanism. Furthermore, protein levels of synaptophysin, syntaxin, and synaptotagmin (synaptic proteins, respectively) were up-regulated by estradiol. We confirmed that the up-regulation of synaptophysin was blocked by the MAPK pathway inhibitor, U0126. These results suggested that estrogen enhanced presynaptic function through the up-regulated exocytotic system. In this study, we propose that estrogen reinforced excitatory synaptic transmission via potentiated-glutamate release from presynaptic sites. 相似文献
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64.
Functional analysis of isoforms of NADPH: protochlorophyllide oxidoreductase (POR), PORB and PORC, in Arabidopsis thaliana 总被引:3,自引:0,他引:3
Masuda T Fusada N Oosawa N Takamatsu K Yamamoto YY Ohto M Nakamura K Goto K Shibata D Shirano Y Hayashi H Kato T Tabata S Shimada H Ohta H Takamiya K 《Plant & cell physiology》2003,44(10):963-974
NADPH:protochlorophyllide oxidoreductase (POR) catalyzes the light-dependent reduction of protochlorophyllide. To elucidate the physiological function of three differentially regulated POR isoforms (PORA, PORB and PORC) in Arabidopsis thaliana, we isolated T-DNA tagged null mutants of porB and porC. The mature seedlings of the mutants had normal photosynthetic competencies, showing that PORB and PORC are interchangeable and functionally redundant in developed plants. In etiolated seedlings, only porB showed a reduction in the photoactive protochlorophyllide and the size of prolamellar bodies (PLBs), indicating that PORB, as well as PORA, functioned in PLB assembly and photoactive protochlorophyllide formation in etiolated seedlings. When illuminated, the etiolated porB seedling was able to green to a similar extent as the wild type, whereas the greening was significantly reduced under low light conditions. During greening, high light irradiation increased the level of PORC protein, and the greening of porC was repressed under high light conditions. The porB, but not porC, etiolated seedling was more sensitive to the far-red block of greening than the wild type, which is caused by depletion of endogenous POR proteins resulting in photo-oxidative damage. These results suggest that, at the onset of greening, PLBs are important for efficient capture of light energy for photoconversion under various light conditions, and PORC, which is induced by high light irradiation, contributes to photoprotection during greening of the etiolated seedlings. 相似文献
65.
Isolation and characterization of a sulfur-oxidizing chemolithotroph growing on crude oil under anaerobic conditions 总被引:1,自引:0,他引:1
Molecular approaches have shown that a group of bacteria (called cluster 1 bacteria) affiliated with the epsilon subclass of the class Proteobacteria constituted major populations in underground crude-oil storage cavities. In order to unveil their physiology and ecological niche, this study isolated bacterial strains (exemplified by strain YK-1) affiliated with the cluster 1 bacteria from an oil storage cavity at Kuji in Iwate, Japan. 16S rRNA gene sequence analysis indicated that its closest relative was Thiomicrospira denitrificans (90% identity). Growth experiments under anaerobic conditions showed that strain YK-1 was a sulfur-oxidizing obligate chemolithotroph utilizing sulfide, elemental sulfur, thiosulfate, and hydrogen as electron donors and nitrate as an electron acceptor. Oxygen also supported its growth only under microaerobic conditions. Strain YK-1 could not grow on nitrite, and nitrite was the final product of nitrate reduction. Neither sugars, organic acids (including acetate), nor hydrocarbons could serve as carbon and energy sources. A typical stoichiometry of its energy metabolism followed an equation: S(2-) + 4NO(3)(-) --> SO(4)(2-) + 4NO(2)(-) (Delta G(0) = -534 kJ mol(-1)). In a difference from other anaerobic sulfur-oxidizing bacteria, this bacterium was sensitive to NaCl; growth in medium containing more than 1% NaCl was negligible. When YK-1 was grown anaerobically in a sulfur-depleted inorganic medium overlaid with crude oil, sulfate was produced, corresponding to its growth. On the contrary, YK-1 could not utilize crude oil as a carbon source. These results suggest that the cluster 1 bacteria yielded energy for growth in oil storage cavities by oxidizing petroleum sulfur compounds. Based on its physiology, ecological interactions with other members of the groundwater community are discussed. 相似文献
66.
67.
68.
Kubota Y Takisawa H 《BioEssays : news and reviews in molecular, cellular and developmental biology》2003,25(4):313-316
Under certain conditions, the cell cycle can be arrested for a long period of time. Vertebrate oocytes are arrested at G(2) phase, while somatic cells arrest at G(0) phase. In both cells, nuclei have lost the ability to initiate DNA synthesis. In a pair of recently published papers,[1,2] Méchali and colleagues and Coué and colleagues have clarified how frog oocytes prevent untimely DNA synthesis during the long G(2) arrest. Intriguingly, they found only Cdc6 is responsible for the inability of immature oocytes to replicate DNA. Cdc6 is a key component for replication licensing, and for G(0) cells to re-enter the proliferative stage. Strikingly similar strategies for preventing the untimely replication in both cells suggest that the suppression of replication licensing is a universal mechanism for securing the prolonged arrest of the cell cycle. 相似文献
69.
Gross structural changes and neuropil formation in the brain during development were described in Idiosepius paradoxus, a sepioid that we chose as a model cephalopod. The brain originates in 4 pairs of ectodermal placodes, which occur separately in the embryonic surface undergoing epiboly. In the final period of epiboly, neuroblasts internalize from the placodes and gather into 4 pairs of ganglionic masses. The ganglionic masses assemble into a ring-like cluster encircling the inner yolk and the foregut anlage, gradually integrated into the 4 domains of a massive brain, a subesophageal mass (SBM), a supraesophageal mass (SPM), and a pair of optic lobes. In the early brain, neuropil forms a framework composed of a longitudinal ladder lying in the SBM, and a transverse arch standing on the lateral sides of the SBM and crossing the SPM. Differentiation of brain lobes proceeds from ventral to dorsal along this framework; first the magnocellular lobes and the posterior pedal lobe appear first in the SBM, the other lobes in the SBM and the basal lobes follow in the proximal region of the SPM, and the accessory lobes develop last in the most dorsal zone of the SPM. In the hatchlings, the brain lobes show almost the same arrangement as in the adults, but the accessory lobes, particularly the vertical lobe, are much smaller than those in the adults. Comparison of the present results with those in the teuthoid and the octopod indicates that developmental sequences of the brain are highly conserved in the coleoid cephalopods. 相似文献
70.
Oku H Futamori N Masuda K Shimabukuro Y Omine T Iwasaki H 《Bioscience, biotechnology, and biochemistry》2003,67(10):2106-2114
It was found that the partially purified beta-ketoacyl-ACP synthase of Bacillus insolitus did not require the addition of FabD (malonyl-CoA:ACP transacylase, MAT) for the activity assay. This study therefore examined the necessity of FabD protein for in vitro branched-chain fatty acid (BCFA) biosynthesis by crude fatty acid synthetases (FAS) of Bacilli. To discover the involvement of FabD in the BCFA biosynthesis, the protein was removed from the crude FAS by immunoprecipitation. The His-tag fusion protein FabD of Bacillus subtilis was expressed in Escherichia coli and used for the preparation of antibody. The rabbit antibody raised against the expressed fusion protein specifically recognized the FabD in the crude FAS of B. subtilis. Evaluation of the efficacy of the immunoprecipitation showed that a trace of FabD protein was present in the antibody-treated crude FAS. However, this complete removal of FabD from the crude FAS did not abolish its BCFA biosynthesis, but only reduced the level to 50-60% of the control level for acyl-CoA primer and to 80% for alpha-keto-beta-methylvalerate primer. Furthermore, the FabD concentration did not necessarily correlate with the MAT specific activity in the enzyme fractions, suggesting the presence of another enzyme source of MAT activity. This study, therefore, suggests that FabD is not the sole enzyme source of MAT for in vitro BCFA biosynthesis, and implies the existence of a functional connection between fatty acid biosynthesis and another metabolic pathway. 相似文献