Citrulline and DRIP-1 Protein (ArgE Homologue) in Drought Tolerance of Wild Watermelon |
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Authors: | YOKOTA AKIHO; KAWASAKI SHINJI; IWANO MEGUMI; NAKAMURA CHIE; MIYAKE CHIKAHIRO; AKASHI KINYA |
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Institution: | 1Department of Molecular Biology, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 89165 Takayama, Ikoma, Nara 6300101, Japan |
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Abstract: | Drought-affected plants experience more than just desiccationof their organs due to water deficit. Plants transpire 1000times more molecules of water than of CO2 fixed by photosynthesisin full sunlight. One effect of transpiration is to cool theleaves. Accordingly, drought brings about such multi-stressesas high temperatures, excess photoradiation and other factorsthat affect plant viability. Wild watermelon serves as a suitablemodel system to study drought responses of C3 plants, sincethis plant survives drought by maintaining its water contentwithout any wilting of leaves or desiccation even under severedrought conditions. Under drought conditions in the presenceof strong light, wild watermelon accumulates high concentrationsof citrulline, glutamate and arginine in its leaves. The accumulationof citrulline and arginine may be related to the induction ofDRIP-1, a homologue of ArgE in Escherichia coli, where it functionsto incorporate the carbon skeleton of glutamate into the ureacycle. Immunogold electron microscopy reveals the enzyme tobe confined exclusively to the cytosol. DRIP-1 is also inducedby treating wild watermelon with 150 mM NaCl, but is not inducedfollowing treatment with 100 µM abscisic acid. The salttreatment causes the accumulation of -aminobutyrate, glutamineand alanine, in addition to a smaller amount of citrulline.Citrulline may function as a potent hydroxyl radical scavenger. |
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Keywords: | Wild watermelon (Citrullus lanatus L ) drought photosynthesis electron sink active oxygen ascorbate peroxidase citrulline arginine -aminobutyrate" target="_blank">gif" ALT="{gamma}" BORDER="0">-aminobutyrate ArgE |
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