Acclimation to low [lsqb]CO sub(2)[rsqb] by an inorganic carbon-concentrating mechanism in Cyanophora paradoxa

• Published in: Plant, cell and environment cell and environment, 2007-11, Vol.30 (11), p.1422-1435
• Main Authors: BUREY, S C, POROYKO, V, Ergen, Z N, Fathi-Nejad, S, Schuller, C, Ohnishi, N, Fukuzawa, H, Bohnert, Hj, LOFFELHARDT, W
• Format: Article
• Language: English
• Subjects: Chlamydomonas reinhardtii; Cyanophora paradoxa; Cyanophyta; Synechocystis
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/j.1365-3040.2007.01715.x

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 sub(2) exchange activity as well as apparent affinity against inorganic carbon were found to increase under CO sub(2)-limiting stress. Further, expressed sequence tags (ESTs) of C. paradoxa were obtained from two cDNA libraries, one from cells grown in high [lsqb]CO sub(2)[rsqb] conditions and one from cells grown under low [lsqb]CO sub(2)[rsqb] conditions. A cDNA microarray platform assembled from 2378 cDNA sequences revealed that 142 genes significantly responded to a shift from high to low [lsqb]CO sub(2)[rsqb]. 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 [lsqb]CO sub(2)[rsqb], 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.