Saccharomyces cerevisiae normally cannot assimilate mannitol, a promising brown macroalgal carbon source for bioethanol production. The molecular basis of this inability remains unknown. We found that cells capable of assimilating mannitol arose spontaneously from wild-type S. cerevisiae during prolonged culture in mannitol-containing medium. Based on microarray data, complementation analysis, and cell growth data, we demonstrated that acquisition of mannitol-assimilating ability was due to spontaneous mutations in the genes encoding Tup1 or Cyc8, which constitute a general corepressor complex that regulates many kinds of genes. We also showed that an S. cerevisiae strain carrying a mutant allele of CYC8 exhibited superior salt tolerance relative to other ethanologenic microorganisms; this characteristic would be highly beneficial for the production of bioethanol from marine biomass. Thus, we succeeded in conferring the ability to assimilate mannitol on S. cerevisiae through dysfunction of Tup1-Cyc8, facilitating production of ethanol from mannitol. Macroalgae, consisting of green, red, and brown algae, are promising sources of biofuels for several reasons: (i) macroalgae are more productive than land crops; (ii) arable land is not required for algal cultivation, obviating the necessity for irrigation, fertilizer, etc.; and (iii) macroalgae contain no lignin (1-4). Both red and brown algae contain high levels of carbohydrates, and a method for producing biofuel from these carbohydrates would be of tremendous economic and environmental benefit.Brown macroalgae contain up to 33% (wt/wt [dry weight]) mannitol, which is the sugar alcohol corresponding to mannose and a promising carbon source for bioethanol production (1, 5, 6). Although some bacteria, such as Escherichia coli and Zymobacter palmae, can assimilate mannitol, i.e., utilize mannitol and produce ethanol (6, 7), bacteria are generally sensitive to ethanol, as well as, several other growth-inhibitory compounds. Z. palmae and E. coli KO11 can produce ca. 1.3% (wt/vol) and 2.6% (wt/vol) ethanol from 3.8% (wt/vol) and 9.0% (wt/vol) mannitol, respectively; however, both strains are sensitive to 5% (wt/vol) ethanol (8,9). Yeast is currently considered to have several advantages over ethanologenic bacteria, including high tolerance to ethanol and inhibitory compounds (10). Several yeast strains, such as Pichia angophorae and Saccharomyces paradoxus NBRC0259-3, can produce ethanol from mannitol (8, 11). However, compared to the well-characterized model organism Saccharomyces cerevisiae, the host-vector systems of these yeasts are not well equipped, and their genetics and physiologies are poorly defined.Mannitol dehydrogenase is the key enzyme that catalyzes the pyridine nucleotide-dependent oxidation of D-mannitol to Dfructose (12). Despite the existence of genes encoding putative homologs of mannitol dehydrogenase (YEL070W and YNR073C), S. cerevisiae strains, including the S288C reference strain, are unable to assimilate mannitol for growth; a few exceptions exi...

We report that the cubic octameric polyhedral oligomeric silsesquioxanes (POSS)-core dendrimers, novel gadolinium (Gd) chelators, enhanced the proton relaxivity to Gd 3þ . The stability of the Gd complex with POSS(G1.5) was similar to those of DOTA and DTPA. From the MTT assay with the primary hepatocytes, the cytotoxicity of [Gd 2 POSS(G1.5)]2À showed lower than that of the [Gd(DOTA)]À complex. The detection limits were approximately 100-fold improved than those of DOTA and DTPA-Gd complexes in the MR images.KEY WORDS: MRI / Contrast Agent / Silsesquioxane / Dendrimer / Gadolinium / POSS / Magnetic resonance imaging (MRI) is one of powerful diagnostic tools in modern clinical medicine, and paramagnetic complexes, which have the ability to enhance the proton relaxation rate of water tissue, are used as contrast agents for improving sensitivity and specificity. The most commonly used positive contrast agents nowadays are thermodynamically and kinetically stable low molecular weight gadolinium compounds based on a polyaminocarboxylate motif (linear DTPA and cyclic DOTA respectively) for suppressing the toxicity of Gd 3þ and accelerating the proton relaxation rate of water tissue coordinated to Gd 3þ . 1 Since contrast agents with high relaxivity can be detected at lower doses, the relaxation mechanism and a number of predominant parameters to achieve sufficient T 1 change have been studied.

A methanol extract of Alsomitra macrocarpa leaves and branches induced a marked alteration of cell morphology in a human stellate cell line (LX-2). Similar morphologic alterations were observed in several other cell lines. Active compound was purified from the extract and determined to be cucurbitacin E (Cuc E). It has been known that Cuc E causes marked disruption of the actin cytoskeleton, supporting our observation, but how Cuc E altered the actin cytoskeleton has not been elucidated. By using the standard fluorescence assay using copolymerization and depolymerization of native and pyrene labelled actin, this study revealed that Cuc E interacted directly with actin consequently stabilizing the polymerized actin. When NIH-3T3 cells exogenously expressing YFP-labeled actin were treated with Cuc E, firstly the aggregation of globular actin and secondly the aggregation of actin including disrupted fibrous actin in the cells was observed.

Background: HIRA is a conserved histone chaperone required for regulation of chromatin structure. Results: Genes that encode HIRA proteins are responsible for cross-tolerance. Specifically, stress-responsive gene expression was most profoundly compromised in HIRA disruptants. Conclusion: HIRA is involved in cross-tolerance via regulation of stress-responsive gene expression. Significance: This study provides evidence that fission yeast HIRA functions in stress response.

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