title: Increased thermostability of thylakoid membranes in isoprene-emitting leaves probed with three biophysical techniques.
abstract: Three biophysical approaches were used to get insight into increased thermostability of thylakoid membranes in isoprene-emittingplants.Arabidopsis (Arabidopsis thaliana) plants genetically modified to make isoprene and Platanus orientalis leaves, in which isoprene emission was chemically inhibited, were used. First, in the circular dichroism spectrum the transition temperature of the main band at 694 nm was higher in the presence of isoprene, indicating that the heat stability of chiral macrodomains of chloroplast membranes, and specifically the stability of ordered arrays of light-harvesting complex II-photosystem II in the stacked region of the thylakoid grana, was improved in the presence of isoprene. Second, the decay of electrochromic absorbance changes resulting from the electric field component of the proton motive force (ΔA₅₁₅) was evaluated following single-turnover saturating flashes. The decay of ΔA₅₁₅ was faster in the absence of isoprene when leaves of Arabidopsis and Platanus were exposed to high temperature, indicating that isoprene protects the thylakoid membranes against leakiness at elevated temperature. Finally, thermoluminescence measurements revealed that S₂Q(B)⁻ charge recombination was shifted to higher temperature in Arabidopsis and Platanus plants in the presence of isoprene, indicating higher activation energy for S₂Q(B)⁻ redox pair, which enables isoprene-emitting plants to perform efficient primary photochemistry of photosystem II even at higher temperatures. The data provide biophysical evidence that isoprene improves the integrity and functionality of the thylakoid membranes at high temperature. These results contribute to our understanding of isoprene mechanism of action in plant protection against environmental stresses.
authors.affiliation: Institute of Plant Physiology and Genetics , Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria.
authors.forename: Violeta
authors.initials: V
authors.lastname: Velikova
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Várkonyi
authors.forename: Milán
authors.initials: M
authors.lastname: Szabó
authors.forename: Liliana
authors.initials: L
authors.lastname: Maslenkova
authors.forename: Isabel
authors.initials: I
authors.lastname: Nogues
authors.forename: László
authors.initials: L
authors.lastname: Kovács
authors.forename: Violeta
authors.initials: V
authors.lastname: Peeva
authors.forename: Mira
authors.initials: M
authors.lastname: Busheva
authors.forename: Gyozo
authors.initials: G
authors.lastname: Garab
authors.forename: Thomas D
authors.initials: TD
authors.lastname: Sharkey
authors.forename: Francesco
authors.initials: F
authors.lastname: Loreto
mesh_terms: D019883:Alkyl and Aryl Transferases / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D001703:Biophysics / Q000379:methods*; D002070:Butadienes / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism; D002942:Circular Dichroism; D045782:Hemiterpenes / Q000378:metabolism*; D006358:Hot Temperature; D045342:Light-Harvesting Protein Complexes / Q000032:analysis; D019684:Magnoliopsida / Q000378:metabolism*; D010420:Pentanes / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000032:analysis; D018515:Plant Leaves / Q000378:metabolism*; D030821:Plants, Genetically Modified; D029908:Pueraria / Q000201:enzymology / Q000235:genetics; D020524:Thylakoids / Q000737:chemistry* / Q000378:metabolism; D014197:Trees
chemical_list: D002070:Butadienes; D045782:Hemiterpenes; D045342:Light-Harvesting Protein Complexes; D010420:Pentanes; D045332:Photosystem II Protein Complex; C005059:isoprene; D019883:Alkyl and Aryl Transferases; C093854:isoprene synthase