title: Antisense reductions in the PsbO protein of photosystem II leads to decreased quantum yield but similar maximal photosynthetic rates.
abstract: Photosystem (PS) II is the multisubunit complex which uses light energy to split water, providing the reducing equivalents needed for photosynthesis. The complex is susceptible to damage from environmental stresses such as excess excitation energy and high temperature. This research investigated the in vivo photosynthetic consequences of impairments to PSII in Arabidopsis thaliana (ecotype Columbia) expressing an antisense construct to the PsbO proteins of PSII. Transgenic lines were obtained with between 25 and 60% of wild-type (WT) total PsbO protein content, with the PsbO1 isoform being more strongly reduced than PsbO2. These changes coincided with a decrease in functional PSII content. Low PsbO (less than 50% WT) plants grew more slowly and had lower chlorophyll content per leaf area. There was no change in content per unit area of cytochrome b6f, ATP synthase, or Rubisco, whereas PSI decreased in proportion to the reduction in chlorophyll content. The irradiance response of photosynthetic oxygen evolution showed that low PsbO plants had a reduced quantum yield, but matched the oxygen evolution rates of WT plants at saturating irradiance. It is suggested that these plants had a smaller pool of PSII centres, which are inefficiently connected to antenna pigments resulting in reduced photochemical efficiency.
authors.affiliation: Research School of Biology, The Australian National University, Canberra ACT 0200, Australia.
authors.forename: Simon A
authors.initials: SA
authors.lastname: Dwyer
authors.forename: Wah Soon
authors.initials: WS
authors.lastname: Chow
authors.forename: Wataru
authors.initials: W
authors.lastname: Yamori
authors.forename: John R
authors.initials: JR
authors.lastname: Evans
authors.forename: Sarah
authors.initials: S
authors.lastname: Kaines
authors.forename: Murray R
authors.initials: MR
authors.lastname: Badger
authors.forename: Susanne
authors.initials: S
authors.lastname: von Caemmerer
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology / Q000528:radiation effects / Q000648:ultrastructure; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism / Q000648:ultrastructure; D008027:Light; D010100:Oxygen / Q000378:metabolism*; D010641:Phenotype; D010788:Photosynthesis / Q000502:physiology*; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018515:Plant Leaves / Q000235:genetics / Q000502:physiology / Q000528:radiation effects / Q000648:ultrastructure; D030821:Plants, Genetically Modified; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D016372:RNA, Antisense / Q000235:genetics*; D018749:RNA, Plant / Q000235:genetics
chemical_list: D045332:Photosystem II Protein Complex; D020033:Protein Isoforms; D016372:RNA, Antisense; D018749:RNA, Plant; C054266:photosystem II manganese-stabilizing protein; D002734:Chlorophyll; D010100:Oxygen