Fatty acid synthesis system in Glaucophyta: Further evidence for the lack of chloroplast fatty acid synthesis in glaucophyte algae

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Abstract
We previously showed that the chloroplast of the glaucophyte Cyanophora paradoxa does not have fatty acid synthesis activity, based on both experimental and bioinformatic analyses. The present study was intended to extend the bioinformatic analysis to a wider range of Glaucophyta, using published genomic data. The results confirmed that the four species of Glaucophyta analyzed do not have prokaryotic acetyl-CoA carboxylase, which is found in the chloroplasts of Rhodophyta and Viridiplantae. Only the eukaryotic type of acetyl-CoA carboxylase was identified. Some components of prokaryotic fatty acid synthase (FAS II), such as acyl carrier protein (ACP), 2-oxoacyl ACP synthase (KAS I/II), and FabD, were detected in the glaucophytes, but other components especially KAS III were not detected. In contrast, the eukaryotic fatty acid synthase (FAS I) was found in Gloeochaete as well as Cyanophora. Although the genome data is still to be amended, the available evidence suggests that the lack of fatty acid synthesis in the chloroplast is a trait of not just Cyanophora but also shared by the phylum Glaucophyta. The relationship between photosynthesis and fatty acid synthesis is discussed with special attention to the origin of chloroplasts.

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