The Liverwort,Marchantia, Drives Alternative Electron Flow Using a Flavodiiron Protein to Protect PSI.
The diffusion efficiency of oxygen in the atmosphere, like that of CO2, is approximately 104times greater than that in aqueous environments. Consequently, terrestrial photosynthetic organisms need mechanisms to protect against potential oxidative damage. The liverwortMarchantia polymorpha, a basal land plant, has habitats where it is exposed to both water and the atmosphere. Furthermore, like cyanobacteria,M. polymorphahas genes encoding flavodiiron proteins (FLV). In cyanobacteria, FLVs mediate oxygen-dependent alternative electron flow (AEF) to suppress the production of reactive oxygen species. Here, we investigated whether FLVs are required for the protection of photosynthesis inM. polymorphaA mutant deficient in the FLV1 isozyme (ΔMpFlv1) sustained photooxidative damage to photosystem I (PSI) following repetitive short-saturation pulses of light. Compared with the wild type (Takaragaike-1), ΔMpFlv1showed the same photosynthetic oxygen evolution rate but a lower electron transport rate during the induction phase of photosynthesis. Additionally, the reaction center chlorophyll in PSI, P700, was highly reduced in ΔMpFlv1but not in Takaragaike-1. These results indicate that the gene product ofMpFlv1drives AEF to oxidize PSI, as in cyanobacteria. Furthermore, FLV-mediated AEF supports the production of a proton motive force to possibly induce the nonphotochemical quenching of chlorophyll fluorescence and suppress electron transport in the cytochromeb6/fcomplex. After submerging the thalli, a decrease in photosystem II operating efficiency was observed, particularly in ΔMpFlv1, which implies that species living in these sorts of habitats require FLV-mediated AEF.
Graduate School of Agricultural Science (G.S., M.T., T.S., C.M.) and Graduate School of Science (K.I., S.T.), Kobe University, Nada, Kobe 657-8501, Japan; and.|Core Research for Environmental Science and Technology, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076, Japan (C.M.).
Ginga
0000-0002-8557-2096
G
Shimakawa
Graduate School of Agricultural Science (G.S., M.T., T.S., C.M.) and Graduate School of Science (K.I., S.T.), Kobe University, Nada, Kobe 657-8501, Japan; and.|Core Research for Environmental Science and Technology, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076, Japan (C.M.).
Kimitsune
0000-0003-0504-8196
K
Ishizaki
Graduate School of Agricultural Science (G.S., M.T., T.S., C.M.) and Graduate School of Science (K.I., S.T.), Kobe University, Nada, Kobe 657-8501, Japan; and.|Core Research for Environmental Science and Technology, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076, Japan (C.M.).
Shigeyuki
S
Tsukamoto
Graduate School of Agricultural Science (G.S., M.T., T.S., C.M.) and Graduate School of Science (K.I., S.T.), Kobe University, Nada, Kobe 657-8501, Japan; and.|Core Research for Environmental Science and Technology, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076, Japan (C.M.).
Moeko
0000-0002-5318-3707
M
Tanaka
Graduate School of Agricultural Science (G.S., M.T., T.S., C.M.) and Graduate School of Science (K.I., S.T.), Kobe University, Nada, Kobe 657-8501, Japan; and.|Core Research for Environmental Science and Technology, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076, Japan (C.M.).
Takehiro
T
Sejima
Graduate School of Agricultural Science (G.S., M.T., T.S., C.M.) and Graduate School of Science (K.I., S.T.), Kobe University, Nada, Kobe 657-8501, Japan; and cmiyake@hawk.kobe-u.ac.jp.|Core Research for Environmental Science and Technology, Japan Science and Technology Agency, Chiyoda-ku, Tokyo 102-0076, Japan (C.M.) cmiyake@hawk.kobe-u.ac.jp.
Chikahiro
0000-0002-2426-2377
C
Miyake
D002734:Chlorophyll / Q000378:metabolism; D045346:Cytochrome b6f Complex / Q000235:genetics / Q000378:metabolism; D004579:Electron Transport / Q000235:genetics; D005420:Flavoproteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008027:Light; D047008:Marchantia / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010100:Oxygen / Q000378:metabolism; D010788:Photosynthesis / Q000235:genetics / Q000528:radiation effects; D045331:Photosystem I Protein Complex / Q000235:genetics / Q000378:metabolism*; D045332:Photosystem II Protein Complex / Q000235:genetics / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018892:Proton-Motive Force / Q000528:radiation effects; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
D005420:Flavoproteins; D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex; D010940:Plant Proteins; D002734:Chlorophyll; D045346:Cytochrome b6f Complex; D010100:Oxygen