Grana-Localized Proteins, RIQ1 and RIQ2, Affect the Organization of Light-Harvesting Complex II and Grana Stacking in Arabidopsis.
Grana are stacked thylakoid membrane structures in land plants that contain PSII and light-harvesting complex II proteins (LHCIIs). We isolated twoArabidopsis thalianamutants,reduced induction of non-photochemical quenching1(riq1) andriq2, in which stacking of grana was enhanced. Thecurvature thylakoid 1a(curt1a) mutant was previously shown to lack grana structure. Inriq1 curt1a, the grana were enlarged with more stacking, and inriq2 curt1a, the thylakoids were abnormally stacked and aggregated. Despite having different phenotypes in thylakoid structure,riq1,riq2, andcurt1ashowed a similar defect in the level of nonphotochemical quenching of chlorophyll fluorescence (NPQ). Inriq curt1adouble mutants, NPQ induction was more severely affected than in either single mutant. Inriqmutants, state transitions were inhibited and the PSII antennae were smaller than in wild-type plants. Theriqdefects did not affect NPQ induction in the chlorophyllb-less mutant.RIQ1andRIQ2are paralogous and encode uncharacterized grana thylakoid proteins, but despite the high level of identity of the sequence, the functions of RIQ1 and RIQ2 were not redundant. RIQ1 is required for RIQ2 accumulation, and the wild-type level of RIQ2 did not complement the NPQ and thylakoid phenotypes inriq1We propose that RIQ proteins link the grana structure and organization of LHCIIs.
Department of Botany, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.
Ryo
R
Yokoyama
Department of Botany, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan.|Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076, Japan.
Hiroshi
H
Yamamoto
Department of Cell Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan.|Spectrography and Bioimaging Facility, National Institute for Basic Biology, Okazaki 444-8585, Japan.
Maki
M
Kondo
Department of Biological Science, Graduate School of Science, Osaka Prefecture University, Sakai 599-8531, Japan.
Satomi
S
Takeda
Graduate School of Biostudies, Kyoto University, Sakyo-ku, Kyoto 606-8502 Japan.
Kentaro
K
Ifuku
Department of Bioinformatics, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
Yoichiro
Y
Fukao
Spectrography and Bioimaging Facility, National Institute for Basic Biology, Okazaki 444-8585, Japan.
Yasuhiro
Y
Kamei
Department of Cell Biology, National Institute for Basic Biology, Okazaki 444-8585, Japan.
Mikio
M
Nishimura
Department of Botany, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan shikanai@pmg.bot.kyoto-u.ac.jp.|Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076, Japan.
Toshiharu
T
Shikanai