Prolamellar bodies formed by cyanobacterial protochlorophyllide oxidoreductase in Arabidopsis.
In angiosperms, chlorophyll biosynthesis is light dependent. A key factor in this process is protochlorophyllide oxidoreductase (POR), which requires light to catalyze the reduction of protochlorophyllide to chlorophyllide. It is believed that this protein originated from an ancient cyanobacterial enzyme that was introduced into proto-plant cells during the primary symbiosis. Here we report that PORs from the cyanobacteria Gloeobacter violaceus PCC7421 and Synechocystis sp. PCC6803 function in plastids. First, we found that the G. violaceus POR shows a higher affinity to its substrate protochlorophyllide than the Synechocystis POR but a similar affinity to plant PORs. Secondly, the reduced size of prolamellar bodies caused by a knockdown mutation of one of the POR genes, PORA, in Arabidopsis could be complemented by heterologous expression of the cyanobacterial PORs. Photoactive protochlorophyllide in the etioplasts of the complementing lines, however, was retained at a low level as in the parent PORA knockdown mutant, indicating that the observed formation of prolamellar bodies was irrelevant to the assembly of photoactive protochlorophyllide. This work reveals a new view on the formation of prolamellar bodies and provides new clues about the function of POR in the etioplast-chloroplast transition.
Masuda
Shinji
S
Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama 226-8501, Japan. shmasuda@bio.titech.ac.jp
Ikeda
Rei
R
Masuda
Tatsuru
T
Hashimoto
Haruki
H
Tsuchiya
Tohru
T
Kojima
Hiroko
H
Nomata
Jiro
J
Fujita
Yuichi
Y
Mimuro
Mamoru
M
Ohta
Hiroyuki
H
Takamiya
Ken-Ichiro
K
D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000201:enzymology* / Q000235:genetics; D002734:Chlorophyll / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism / Q000648:ultrastructure; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D055785:Gene Knockdown Techniques; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D044925:Oxidoreductases Acting on CH-CH Group Donors / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism; D011521:Protochlorophyllide / Q000378:metabolism*; D018749:RNA, Plant / Q000378:metabolism; D046939:Synechocystis / Q000201:enzymology* / Q000235:genetics
D018749:RNA, Plant; D002734:Chlorophyll; D011521:Protochlorophyllide; D044925:Oxidoreductases Acting on CH-CH Group Donors