| Budget Amount *help |
¥3,910,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥210,000)
Fiscal Year 2007: ¥910,000 (Direct Cost: ¥700,000、Indirect Cost: ¥210,000)
Fiscal Year 2006: ¥3,000,000 (Direct Cost: ¥3,000,000)
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| Research Abstract |
We investigated changes of trehalose level in field-isolated, natural colonies of the terrestrial cyanobacterium Nostoc commune responding to desiccation. No detectable trehalose was found in fully hydrated N. commune colonies; however, trehalose accumulation occurred in response to water loss during desiccation and high levels of trehalose were detected in the air-dried colonies. The three genes for trehalose metabolism, treZ (maltooligosyltrehalose trehalohydrolase, Mth), treY (maltooligosyltrehalose synthase, Mts), and treH (trehalase), were found as a gene cluster, and the mRNAs for these genes were detectable at similar levels during desiccation. Trehalase of N. punctiforme was heterologously expressed in E. coli cells in an active form with a molecular mass of 52kDa. Trehalase activity was strongly inhibited in the presence of 10mM NaCl while trehalose synthesis activity remained active in the presence of salt. These data suggest that the rate of trehalose production exceeds that of trehalose hydrolysis under water-stress conditions characterized by increased cellular solute concentrations. The terrestrial cyanobacterium N. commune forms a visible colony in which the cells are embedded in extracellular polysaccharides (EPSs), which play a crucial role in the extreme desiccation tolerance of this organism. The activities that hydrolyse glycoside bonds were examined using artificial nitrophenyl-linked sugars as substrates. Aβ-D-glucosidase, with a molecular mass of20kDa, was resistant to20min of boiling and was identified as a cyanobacterial fasciclin protein based on its N-terminal amino-acid sequence. The36-kDa major protein (WspA) showed heat-resistantβ-D-galactosidase activity.
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