title: Direct transcriptional control of the chloroplast genes psbA and psaAB adjusts photosynthesis to light energy distribution in plants.
abstract: Two photosystems, I and II, absorb and convert light energy in photosynthesis in chloroplasts of green plants. The genes psbA and psaAB of the cytoplasmic chloroplast genome encode core components of photosystem II and photosystem I, respectively. Here we show that the absolute amounts of photosystem I and photosystem II respond, in a complementary manner, to changes in light quality that preferentially excite each photosystem in mustard seedlings. We also show that the initial response to altered energy distribution is a change in the rates of transcription of psbA and psaAB. Changes in chlorophyll fluorescence emission in vivo suggest that the signal initiating this change is the oxidation-reduction state of plastoquinone, a component of the photosynthetic electron transport chain that connects photosystem I and photosystem II. The results are consistent with transcriptional effects observed previously with chloroplasts isolated in vitro and demonstrate that redox control of chloroplast transcription initiates long-term adjustments that compensate for imbalance in energy distribution and adapt the whole plant to altered light environments.
authors.affiliation: Lund University, Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Pfannschmidt
authors.forename: A
authors.initials: A
authors.lastname: Nilsson
authors.forename: A
authors.initials: A
authors.lastname: Tullberg
authors.forename: G
authors.initials: G
authors.lastname: Link
authors.forename: J F
authors.initials: JF
authors.lastname: Allen
mesh_terms: D002736:Chloroplasts / Q000502:physiology*; D018506:Gene Expression Regulation, Plant / Q000502:physiology*; D008027:Light; D045342:Light-Harvesting Protein Complexes; D010788:Photosynthesis / Q000235:genetics*; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics*; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D018521:Plant Physiological Phenomena; D010940:Plant Proteins / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins