Cloning and expression of the soybean chlH gene encoding a subunit of Mg-chelatase and localization of the Mg2+ concentration-dependent ChlH protein within the chloroplast.
From the soybean cDNA library, we isolated and analyzed the chlH gene encoding a subunit of Mg-chelatase. The subunit was a polypeptide of 1,383 amino acids with a molecular mass of 153,491 Da, which shared 90% identity with the olive gene from Antirrhinum majus. The regulation of the expression of chlH was investigated in photomix-otrophic soybean suspension cells (SB-P). The expression was light-inducible, and the induction was more rapid than those of chlI and cab2. Furthermore, the levels of the transcripts and products of chlH appeared to be regulated by a circadian oscillation. The subchloroplastic localization of ChlH was investigated by immunoblot analyses with antiserum against recombinant ChlH. Depending on the concentration of Mg2+ in the lysis buffer, the localization of ChlH protein migrated between the stroma and the envelope membrane; ChlH was localized on the envelope membrane, a major site of chlorophyll biosynthesis, when the Mg2+ concentration of the lysis buffer was high (above 5 mM). These results indicated that the activity of Mg-chelatase was regulated by modulation of the expression and subchloroplastic localization of ChlH protein.
Nakayama
M
M
Department of Biological Sciences, Faculty of Bioscience and Biotechnology, Tokyo Institute of Technology, Yokohama, Japan.
Masuda
T
T
Bando
T
T
Yamagata
H
H
Ohta
H
H
Takamiya
K
K
D000595:Amino Acid Sequence; D002451:Cell Compartmentation / Q000187:drug effects; D002734:Chlorophyll / Q000096:biosynthesis; D002736:Chloroplasts / Q000201:enzymology*; D002940:Circadian Rhythm; D003001:Cloning, Molecular; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D008027:Light; D008190:Lyases / Q000235:genetics*; D008274:Magnesium / Q000494:pharmacology; D008969:Molecular Sequence Data; D011166:Porphyrins / Q000378:metabolism; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013025:Glycine max / Q000201:enzymology / Q000235:genetics*
D011166:Porphyrins; D002734:Chlorophyll; D008190:Lyases; C086788:magnesium chelatase; D008274:Magnesium