The AtCAO gene, encoding chlorophyll a oxygenase, is required for chlorophyll b synthesis in Arabidopsis thaliana

Proc Natl Acad Sci U S A. 1999 Aug 31;96(18):10507-11. doi: 10.1073/pnas.96.18.10507.


Chlorophyll b is synthesized from chlorophyll a and is found in the light-harvesting complexes of prochlorophytes, green algae, and both nonvascular and vascular plants. We have used conserved motifs from the chlorophyll a oxygenase (CAO) gene from Chlamydomonas reinhardtii to isolate a homologue from Arabidopsis thaliana. This gene, AtCAO, is mutated in both leaky and null chlorina1 alleles, and DNA sequence changes cosegregate with the mutant phenotype. AtCAO mRNA levels are higher in three different mutants that have reduced levels of chlorophyll b, suggesting that plants that do not have sufficient chlorophyll b up-regulate AtCAO gene expression. Additionally, AtCAO mRNA levels decrease in plants that are grown under dim-light conditions. We have also found that the six major Lhcb proteins do not accumulate in the null ch1-3 allele.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Arabidopsis / enzymology*
  • Arabidopsis / genetics*
  • Base Sequence
  • Chlamydomonas reinhardtii / genetics
  • Chlorophyll / biosynthesis*
  • Gene Expression Regulation, Enzymologic
  • Gene Expression Regulation, Plant*
  • Intracellular Membranes / enzymology
  • Molecular Sequence Data
  • Mutation
  • Organelles / enzymology
  • Oxygenases / chemistry
  • Oxygenases / genetics*
  • Oxygenases / metabolism
  • RNA, Messenger / genetics
  • Sequence Alignment
  • Sequence Homology, Amino Acid
  • Transcription, Genetic


  • RNA, Messenger
  • Chlorophyll
  • chlorophyll b
  • Oxygenases
  • chlorophyll a oxygenase

Associated data

  • GENBANK/AF177200