title: Surface electric charge of thylakoid membranes from genetically modified tobacco plants under freezing stress.
abstract: In the present study we characterize for the first time electrokinetic and light scattering properties of thylakoids from freezing-tolerant tobacco plants, transformed to accumulate osmoprotectants (proline: AtP5Cs, VacP5Cs; fructan: SacB; glycine betaine: codA). Tobacco plants of wild type (WT) and transformed variants were cultivated at 2°C (cold acclimated) and -2°C (freezing stressed). "Lower salt" thylakoids (I=0.0006) of WT and SacB plants exhibited a decrease in electrophoretic mobility (EPM) after (2°C) treatment. AtP5Cs thylakoids (22°C) show a substantial increase in negative electrical charge (σ) upon illumination. We observed that "low salt"SacB thylakoids at 22°C and 2°C increased the σ on their membrane surfaces during the process of acclimation. WT (22°C) and AtP5Cs thylakoids (2°C) in "low salt" media (I=0.0156) showed a substantial increase in surface electrical charge upon illumination. Cold acclimation on WT and freezing stress on transformed plants resulted in a decrease in aggregation of thylakoids at both ionic strengths. There was a large enhancement in the relaxation capacity of reverse photosynthetic reactions in codA and SacB tobacco after freezing stress. Maximal intensity of the delayed light emission following low temperature stimuli was decreased, revealing a path for tobacco transformants to improve their cold stress tolerance. Here, we suggest the EPM value as an indicator for stability of thylakoids undergone genetic transformation.
authors.affiliation: Department of Biophysics and Radiobiology, Faculty of Biology, 8 Dragan Tzankov Blvd., Sofia University St. Kliment Ohridski, 1164 Sofia, Bulgaria. virjird@biofac.uni-sofia.bg
authors.forename: Virjinia
authors.initials: V
authors.lastname: Doltchinkova
authors.forename: Plamena
authors.initials: P
authors.lastname: Angelova
authors.forename: Elitsa
authors.initials: E
authors.lastname: Ivanova
authors.forename: Dimiter
authors.initials: D
authors.lastname: Djilianov
authors.forename: Daniela
authors.initials: D
authors.lastname: Moyankova
authors.forename: Tatyana
authors.initials: T
authors.lastname: Konstantinova
authors.forename: Atanas
authors.initials: A
authors.lastname: Atanassov
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D001622:Betaine / Q000378:metabolism; D002338:Carotenoids / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D005615:Freezing; D005630:Fructans / Q000235:genetics / Q000378:metabolism; D008027:Light; D030821:Plants, Genetically Modified; D011392:Proline / Q000235:genetics / Q000378:metabolism; D013312:Stress, Physiological; D020524:Thylakoids / Q000737:chemistry* / Q000378:metabolism; D014026:Nicotiana / Q000166:cytology* / Q000235:genetics
chemical_list: D005630:Fructans; D002734:Chlorophyll; D002338:Carotenoids; D001622:Betaine; D011392:Proline