Chlorophyll a oxygenase (CAO) is involved in chlorophyll b formation from chlorophyll a.
Chlorophyll b is an ubiquitous accessory pigment in land plants, green algae, and prochlorophytes. Its biosynthesis plays a key role in the adaptation to various light environments. We isolated six chlorophyll b-less mutants by insertional mutagenesis by using the nitrate reductase or argininosuccinate lyase genes as tags and examined the rearrangement of mutant genomes. We found that an overlapping region of a nuclear genome was deleted in all mutants and that this encodes a protein whose sequence is similar to those of methyl monooxygenases. This coding sequence also contains putative binding domains for a [2Fe-2S] Rieske center and for a mononuclear iron. The results demonstrate that a chlorophyll a oxygenase is involved in chlorophyll b formation. The reaction mechanism of chlorophyll b formation is discussed.
The Institute of Low Temperature Science, Hokkaido University, Sapporo 0600819, Japan. ayumi@pop.lowtem.hokudai.ac.jp
A
A
Tanaka
H
H
Ito
R
R
Tanaka
N K
NK
Tanaka
K
K
Yoshida
K
K
Okada
D000595:Amino Acid Sequence; D002734:Chlorophyll / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism*; D000077194:Chlorophyll A; D005816:Genetic Complementation Test; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010105:Oxygenases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010641:Phenotype; D015183:Restriction Mapping
D002734:Chlorophyll; C037184:chlorophyll b; D010105:Oxygenases; C115272:chlorophyll a oxygenase; D000077194:Chlorophyll A