title: Brassinosteroids regulate the thylakoid membrane architecture and the photosystem II function.
abstract: Brassinosteroids (BRs) are plant steroid hormones known to positively affect photosynthesis. In this work we investigated the architecture and function of photosynthetic membranes in mature Arabidopsis rosettes of BR gain-of-function (overexpressing the BR receptor BR INSENSITIVE 1 (BRI1), BRI1OE) and loss-of-function (bri1-116 with inactive BRI1 receptor, and constitutive photomorphogenesis and dwarfism (cpd) deficient in BR biosynthesis) mutants. Data from atomic force microscopy, circular dichroism, fluorescence spectroscopy and polarographic determination of oxygen yields revealed major structural (enlarged thylakoids, smaller photosystem II supercomplexes) and functional (strongly inhibited oxygen evolution, reduced photosystem II quantum yield) changes in all the mutants with altered BR response compared to the wild type plants. The recorded thermal dependences showed severe thermal instability of the oxygen yields in the BR mutant plants. Our results suggest that an optimal BR level is required for the normal thylakoid structure and function.
authors.affiliation: Institute of Biophysics and Biomedical Engineering, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 21, 1113 Sofia, Bulgaria. sashka@bio21.bas.bg
authors.forename: S
authors.initials: S
authors.lastname: Krumova
authors.forename: M
authors.initials: M
authors.lastname: Zhiponova
authors.forename: K
authors.initials: K
authors.lastname: Dankov
authors.forename: V
authors.initials: V
authors.lastname: Velikova
authors.forename: K
authors.initials: K
authors.lastname: Balashev
authors.forename: T
authors.initials: T
authors.lastname: Andreeva
authors.forename: E
authors.initials: E
authors.lastname: Russinova
authors.forename: S
authors.initials: S
authors.lastname: Taneva
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D060406:Brassinosteroids / Q000378:metabolism*; D008027:Light; D009154:Mutation; D010788:Photosynthesis / Q000528:radiation effects; D045332:Photosystem II Protein Complex / Q000378:metabolism*; D015398:Signal Transduction; D020524:Thylakoids / Q000378:metabolism* / Q000528:radiation effects
chemical_list: D060406:Brassinosteroids; D045332:Photosystem II Protein Complex
keywords: Brassinosteroids; Fluorescence spectroscopy; Oxygen yield; Photosynthesis; Photosystem II function; Thylakoid membrane