title: Increased Salt and Drought Tolerance by D-Ononitol Production in Transgenic Nicotiana tabacum L.
abstract: A cDNA encoding myo-inositol O-methyltransferase (IMT1) has been transferred into Nicotiana tabacum cultivar SR1. During drought and salt stress, transformants (I5A) accumulated the methylated inositol D-ononitol in amounts exceeding 35 [mu]mol g-1 fresh weight In I5A, photosynthetic CO2 fixation was inhibited less during salt stress and drought, and the plants recovered faster than wild type. One day after rewatering drought-stressed plants, I5A photosynthesis had recovered 75% versus 57% recovery with cultivar SR1 plants. After 2.5 weeks of 250 mM NaCl in hydroponic solution, I5A fixed 4.9 [plus or minus] 1.4 [mu]mol CO2 m-2 s-1, whereas SR1 fixed 2.5 [plus or minus] 0.6 [mu]mol CO2 m-2 s-1. myo-Inositol, the substrate for IMT1, increases in tobacco under stress. Preconditioning of I5A plants in 50 mM NaCl increased D-ononitol amounts and resulted in increased protection when the plants were stressed subsequently with 150 mM NaCl. Pro, Suc, Fru, and Glc showed substantial diurnal fluctuations in amounts, but D-ononitol did not. Plant transformation resulting in stress-inducible, stable solute accumulation appears to provide better protection under drought and salt-stress conditions than strategies using osmotic adjustment by metabolites that are constitutively present.
authors.affiliation: Departments of Biochemistry (E.S., W.C., H.J.B., R.G.J.), Plant Sciences (H.J.B., R.G.J.), and Molecular and Cellular Biology (H.J.B.), The University of Arizona, Tucson, Arizona 85721-0088.
authors.forename: E.
authors.initials: E
authors.lastname: Sheveleva
authors.forename: W.
authors.initials: W
authors.lastname: Chmara
authors.forename: H. J.
authors.initials: HJ
authors.lastname: Bohnert
authors.forename: R. G.
authors.initials: RG
authors.lastname: Jensen