title: Citrulline and DRIP-1 protein (ArgE homologue) in drought tolerance of wild watermelon.
abstract: Drought-affected plants experience more than just desiccation of their organs due to water deficit. Plants transpire 1000 times more molecules of water than of CO2 fixed by photosynthesis in full sunlight. One effect of transpiration is to cool the leaves. Accordingly, drought brings about such multi-stresses as high temperatures, excess photoradiation and other factors that affect plant viability. Wild watermelon serves as a suitable model system to study drought responses of C3 plants, since this plant survives drought by maintaining its water content without any wilting of leaves or desiccation even under severe drought conditions. Under drought conditions in the presence of strong light, wild watermelon accumulates high concentrations of citrulline, glutamate and arginine in its leaves. The accumulation of citrulline and arginine may be related to the induction of DRIP-1, a homologue of ArgE in Escherichia coli, where it functions to incorporate the carbon skeleton of glutamate into the urea cycle. Immunogold electron microscopy reveals the enzyme to be confined exclusively to the cytosol. DRIP-1 is also induced by treating wild watermelon with 150 mM NaCl, but is not induced following treatment with 100 microM abscisic acid. The salt treatment causes the accumulation of gamma-aminobutyrate, glutamine and alanine, in addition to a smaller amount of citrulline. Citrulline may function as a potent hydroxyl radical scavenger.
authors.affiliation: Department of Molecular Biology, Graduate School of Biological Sciences, Nara Institute of Science and Technology, Ikoma, Japan. yokota@bs.aist-nara.ac.jp
authors.forename: Akiho
authors.initials: A
authors.lastname: Yokota
authors.forename: Shinji
authors.initials: S
authors.lastname: Kawasaki
authors.forename: Megumi
authors.initials: M
authors.lastname: Iwano
authors.forename: Chie
authors.initials: C
authors.lastname: Nakamura
authors.forename: Chikahiro
authors.initials: C
authors.lastname: Miyake
authors.forename: Kinya
authors.initials: K
authors.lastname: Akashi
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D000064:Acclimatization / Q000187:drug effects; D000409:Alanine / Q000378:metabolism; D000581:Amidohydrolases / Q000096:biosynthesis / Q000737:chemistry; D001120:Arginine / Q000096:biosynthesis; D019607:Brassicaceae / Q000187:drug effects / Q000502:physiology; D002244:Carbon / Q000378:metabolism; D002956:Citrulline / Q000096:biosynthesis*; D029773:Citrullus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D018553:Cucumis sativus / Q000187:drug effects / Q000502:physiology; D004190:Disasters; D018506:Gene Expression Regulation, Plant; D005973:Glutamine / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000096:biosynthesis; D008027:Light; D008954:Models, Biological; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000187:drug effects / Q000502:physiology; D010940:Plant Proteins / Q000096:biosynthesis* / Q000378:metabolism; D010944:Plants / Q000145:classification / Q000187:drug effects; D012965:Sodium Chloride / Q000494:pharmacology; D014867:Water / Q000494:pharmacology / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
chemical_list: D006360:Heat-Shock Proteins; D010940:Plant Proteins; C417971:dip-1 protein, Citrullus lanatus; D014867:Water; D005973:Glutamine; D002956:Citrulline; D012965:Sodium Chloride; D005680:gamma-Aminobutyric Acid; D000040:Abscisic Acid; D002244:Carbon; D001120:Arginine; D000581:Amidohydrolases; C018732:N-acetylornithine deacetylase; D000409:Alanine; D010100:Oxygen