| Budget Amount *help |
¥63,000,000 (Direct Cost: ¥63,000,000)
Fiscal Year 2009: ¥12,000,000 (Direct Cost: ¥12,000,000)
Fiscal Year 2008: ¥12,000,000 (Direct Cost: ¥12,000,000)
Fiscal Year 2007: ¥13,000,000 (Direct Cost: ¥13,000,000)
Fiscal Year 2006: ¥13,000,000 (Direct Cost: ¥13,000,000)
Fiscal Year 2005: ¥13,000,000 (Direct Cost: ¥13,000,000)
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| Research Abstract |
Plants respond to survive under water-deficit conditions via a series of physiological, cellular, and molecular processes culminating in stress tolerance. Plants accumulate osmolites, such as sugars, amino acids and potassium, during osmotic stress. We identified various transporter genes were upregulated during osmotic stress in Arabidopsis. We analyzed an osmotic stress-inducible sugar transporter, ESL1, from Arabidopsis. ESL1 is mainly expressed in pericycle and xylem parenchyma cells. The fluorescence of ESL1-GFP-fused protein was detected at tonoplast in transgenic plants. Alanine-scanning mutagenesis revealed that an N-terminal LXXXLL motif in ESL1 was essential for its localization at the tonoplast. Transgenic tobacco BY-2 cells expressing mutated ESL1, which was localized at the plasma membrane, showed the uptake ability for monosaccharides. The value of K(m) for glucose uptake activity of mutated ESL1 in the transgenic BY-2 cells was extraordinarily high, and the transport activity was independent from a proton gradient. These results indicate that ESL1 is a low affinity facilitated diffusion transporter. We also analyzed an Arabidopsis stress-inducible potassium transporter, KUP6. The localization of KUP6-GFP was observed at plasma membrane. KUP6-overexpressing transgenic plants showed less transpirational water loss and increased tolerance to drought stress. Furthermore, we also analyzed Arabidopsis stress-inducible transporter-like proteins, Cor413 family, whose expression was regulated by DREB1A during cold stress. COR413-IM1 and COR413-IM2.1 were localized at the chloroplast membrane, while COR413-PM1 was localized at ER. Furthermore, we used both gain- and loss-of-function analysis of a histidine kinase, AHK1, and showed that it acts as a positive regulator in osmotic stress signaling in Arabidopsis. Overexpression of AHK1 improved the drought tolerance of transgenic plants.
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