The chloroplast protein BPG2 functions in brassinosteroid-mediated post-transcriptional accumulation of chloroplast rRNA.
Brassinazole (Brz) is a specific inhibitor of the biosynthesis of brassinosteroids (BRs), which regulate plant organ and chloroplast development. We identified a recessive pale green Arabidopsis mutant, bpg2-1 (Brz-insensitive-pale green 2-1) that showed reduced sensitivity to chlorophyll accumulation promoted by Brz in the light. BPG2 encodes a chloroplast-localized protein with a zinc finger motif and four GTP-binding domains that are necessary for normal chloroplast biogenesis. BPG2-homologous genes are evolutionally conserved in plants, green algae and bacteria. Expression of BPG2 is induced by light and Brz. Chloroplasts of the bpg2-1 mutant have a decreased number of stacked grana thylakoids. In bpg2-1 and bpg2-2 mutants, there was no reduction in expression of rbcL and psbA, but there was abnormal accumulation of precursors of chloroplast 16S and 23S rRNA. Chloroplast protein accumulation induced by Brz was suppressed by the bpg2 mutation. These results indicate that BPG2 plays an important role in post-transcriptional and translational regulation in the chloroplast, and is a component of BR signaling.
Komatsu
Tomoyuki
T
Plant Chemical Biology Research Unit, RIKEN Advanced Science Institute, Wako, Saitama 351-0198, Japan.
Kawaide
Hiroshi
H
Saito
Chieko
C
Yamagami
Ayumi
A
Shimada
Setsuko
S
Nakazawa
Miki
M
Matsui
Minami
M
Nakano
Akihiko
A
Tsujimoto
Masafumi
M
Natsume
Masahiro
M
Abe
Hiroshi
H
Asami
Tadao
T
Nakano
Takeshi
T
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002736:Chloroplasts / Q000378:metabolism* / Q000648:ultrastructure; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D009154:Mutation; D010802:Phylogeny; D018747:RNA, Chloroplast / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000378:metabolism*; D012338:RNA, Ribosomal, 23S / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013256:Steroids / Q000378:metabolism*; D014158:Transcription, Genetic
D029681:Arabidopsis Proteins; D018747:RNA, Chloroplast; D012336:RNA, Ribosomal, 16S; D012338:RNA, Ribosomal, 23S; D013256:Steroids; C551728:BPG2 protein, Arabidopsis; D019204:GTP-Binding Proteins