Acclimation to low [CO(2)] by an inorganic carbon-concentrating mechanism in Cyanophora paradoxa.
The glaucocystophyte Cyanophora paradoxa contains cyanelles, plastids with prokaroytic features such as a peptidoglycan wall and a central proteinaceous inclusion body. While this central body includes the majority of the enzyme ribulose 1,5-bisphosphate carboxylase/oxgenase Rubisco), the presence of a carbon-concentrating mechanism (CCM) in C. paradoxa has only been hypothesized. Here, we present physiological data in support of a CCM: CO(2) exchange activity as well as apparent affinity against inorganic carbon were found to increase under CO(2)-limiting stress. Further, expressed sequence tags (ESTs) of C. paradoxa were obtained from two cDNA libraries, one from cells grown in high [CO(2)] conditions and one from cells grown under low [CO(2)] conditions. A cDNA microarray platform assembled from 2378 cDNA sequences revealed that 142 genes significantly responded to a shift from high to low [CO(2)]. Trends in gene expression were comparable to those reported for Chlamydomonas reinhardtii and the cyanobacterium Synechocystis 6803, both possessing a CCM. Among genes regulated by [CO(2)], transcripts were identified encoding carbonic anhydrases (CAs), Rubisco activase and a putative bicarbonate transporter in C. paradoxa, likely functionally involved in the CCM. These results and the polyhedric appearance of the central body further support the hypothesis of a unique 'eukaryotic carboxysome' in Cyanophora.
Burey
S C
SC
Max F. Perutz Laboratories, University of Vienna, Department of Biochemistry, Dr. Bohr-Gasse 9/5, A-1030 Vienna, Austria.
Poroyko
V
V
Ergen
Z N
ZN
Fathi-Nejad
S
S
Schüller
C
C
Ohnishi
N
N
Fukuzawa
H
H
Bohnert
H J
HJ
Löffelhardt
W
W
D000064:Acclimatization / Q000502:physiology*; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D002478:Cells, Cultured; D044424:Cyanophora / Q000166:cytology / Q000378:metabolism*; D020224:Expressed Sequence Tags; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D015723:Gene Library
D002245:Carbon Dioxide; D002244:Carbon