Pigment shuffling in antenna systems achieved by expressing prokaryotic chlorophyllide a oxygenase in Arabidopsis.
The organization of pigment molecules in photosystems is strictly determined. The peripheral antennae have both chlorophyll a and b, but the core antennae consist of only chlorophyll a in green plants. Furthermore, according to the recent model obtained from the crystal structure of light-harvesting chlorophyll a/b-protein complexes II (LHCII), individual chlorophyll-binding sites are occupied by either chlorophyll a or chlorophyll b. In this study, we succeeded in altering these pigment organizations by introducing a prokaryotic chlorophyll b synthesis gene (chlorophyllide a oxygenase (CAO)) into Arabidopsis. In these transgenic plants (Prochlirothrix hollandica CAO plants), approximately 40% of chlorophyll a of the core antenna complexes was replaced by chlorophyll b in both photosystems. Chlorophyll a/b ratios of LHCII also decreased from 1.3 to 0.8 in PhCAO plants. Surprisingly, these transgenic plants were capable of photosynthetic growth similar to wild type under low light conditions. These results indicate that chlorophyll organizations are not solely determined by the binding affinities, but they are also controlled by CAO. These data also suggest that strict organizations of chlorophyll molecules are not essential for photosynthesis under low light conditions.
Institute of Low Temperature Science, Hokkaido University, Kita-ku, N19 W8, Sapporo 060-0819, Japan.
Masumi
M
Hirashima
Soichirou
S
Satoh
Ryouichi
R
Tanaka
Ayumi
A
Tanaka
D016960:Agrobacterium tumefaciens / Q000235:genetics; D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D002736:Chloroplasts / Q000378:metabolism / Q000648:ultrastructure; D005798:Genes, Bacterial; D017343:Genes, Plant; D008854:Microscopy, Electron; D009154:Mutation; D010105:Oxygenases / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D010788:Photosynthesis; D030821:Plants, Genetically Modified; D019692:Prochlorothrix / Q000201:enzymology / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D014170:Transformation, Genetic
D001426:Bacterial Proteins; D011994:Recombinant Proteins; D002734:Chlorophyll; C037184:chlorophyll b; D010105:Oxygenases; C115272:chlorophyll a oxygenase; D000077194:Chlorophyll A