title: Correlations between the temperature dependence of chlorophyll fluorescence and the fluidity of thylakoid membranes.
abstract: To monitor changes in membrane fluidity in Arabidopsis leaves and thylakoid membranes, we investigated the temperature dependence of a chlorophyll fluorescence parameter, minimum fluorescence (Fo), and calculated the threshold temperature [T(Fo)] at which the rise of the fluorescence level Fo was considered to be started. For the modification of membrane fluidity we took three different approaches: (1) an examination of wild-type leaves initially cultured at room temperature (22°C), then exposed to either a lower (4°C) or higher (35°C) temperature for 5 days; (2) measurements of the shift in T(Fo) by two mutants deficient in fatty acid desaturase genes - fad7 and fad7fad8 and (3) an evaluation of the performance of wild-type plants when leaves were infiltrated with chemicals that modify fluidity. When wild-type plants were grown at 22°C, the T(Fo) was 48.3 ± 0.3°C. Plants that were then transferred to a chamber set at 4 or 35°C showed a shift in their T(Fo) to 42.7 ± 0.9°C or 48.9 ± 0.1°C, respectively. Under low-temperature acclimation, the decline in this putative transition temperature was significantly less in fad7 and fad7fad8 mutants compared with the wild-type. In both leaf and thylakoid samples, values for T(Fo) were reduced in samples treated with benzyl alcohol, a membrane fluidizer, whereas T(Fo) rose in samples treated with dimethylsulfoxide, a membrane rigidifier. These results indicate that the heat-induced rise of chlorophyll fluorescence is strongly correlated with the fluidity of thylakoid membranes.
authors.affiliation: Department of Molecular Biology, Pusan National University, Busan, Korea.
authors.forename: Altanzaya
authors.initials: A
authors.lastname: Tovuu
authors.forename: Ismayil S
authors.initials: IS
authors.lastname: Zulfugarov
authors.forename: Choon-Hwan
authors.initials: CH
authors.lastname: Lee
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics; D002734:Chlorophyll / Q000378:metabolism*; D044943:Fatty Acid Desaturases / Q000235:genetics; D005453:Fluorescence; D008560:Membrane Fluidity; D009154:Mutation; D018515:Plant Leaves / Q000378:metabolism; D013696:Temperature; D020524:Thylakoids / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D002734:Chlorophyll; D044943:Fatty Acid Desaturases; C084083:Fad7 protein, Arabidopsis