Chlorophyll breakdown in Chlorella protothecoides: characterization of degreening and cloning of degreening-related genes

Stefan Hörtensteiner, Joanne Chinner, Philippe Matile, Howard Thomas, Iain Donnison

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48 Citations (SciVal)

Abstract

Chlorella protothecoides cultures grown in a nitrogen-free bleaching medium (BM−N) in the dark rapidly degraded chlorophyll (Chl) to red catabolites. This degreening process was investigated under different growth conditions. Supply of nitrogen to the culture medium (BM+N) inhibited bleaching and the synthesis of catabolites as did the addition to BM−N of cycloheximide or a chelator, 2,2′-bipyridyl. In contrast, chloramphenicol or the protease inhibitor E64 had no effect. During bleaching, Chl breakdown was accompanied by the degradation of cellular proteins such as light-harvesting complex II, cytochrome f and protochlorophyllide oxido-reductase. During growth in BM–N, protease activity increased and proteins immunologically detectable with an antibody against a senescence-enhanced cysteine protease accumulated. cDNAs from BM−N and BM+N cells were used for differential and subtractive screening to isolate cDNAs representing genes with degreening-enhanced expression (dee) in C. protothecoides. Several different dees were identified with different patterns of expression during Chlorella growth but which were all expressed at higher levels during bleaching. Among these, dee4 was most abundant and its expression was exclusive in BM–N cultures. Analysis of the dee sequences showed that they encode different proteins including a novel amino acid carrier (dee4), ferritin, ATP-dependent citrate lyase, a Ca2+-binding protein, MO25, ubiquinone-cytochrome c-reductase and several new proteins.
Original languageEnglish
Pages (from-to)439-450
Number of pages12
JournalPlant Molecular Biology
Volume42
Issue number3
DOIs
Publication statusPublished - Feb 2000

Keywords

  • Chlorella protothecoides
  • Chlorophyll breakdown
  • Degreening
  • Differential screening
  • Senescence
  • cDNA

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