LET THERE BE LIGHT (BUT NOT TOO MUCH): MOLECULAR EVOLUTION OF LIGHT-HARVESTING COMPLEXES

• Published in: Journal of phycology Vol. 36; no. s3; p. 25
• Main Author: Green, B.R.
• Format: Journal Article
• Language: English
• Published: Boston, MA, USA Blackwell Science Inc 01.12.2000
• Subjects: Algae; Brackish; Cyanophyta; Freshwater; Marine
• ISSN: 0022-3646; 1529-8817
• DOI: 10.1046/j.1529-8817.1999.00001-75.x

The light‐harvesting antennas common to all photosynthetic eukaryotes belong to two protein familes: the Chl a‐binding core complex family (e.g. CP47, CP43), and the LHC superfamily, whose members bind a variety of Chls. The former are all chloroplast‐encoded and have high sequence similarity to their cyanobacterial homologs; the latter are all nucleus‐encoded and have a much more complex relationship with each other and their (presumed) cyanobacterial ancestors. Phylogenetic analysis of the LHC superfamily protein sequences show that they follow the endosymbiotic history of their hosts and suggest that the ancestral cyanobacterial genes were copied to the nucleus soon after the establishment of the primary endosymbiosis. Both families have members whose role appears to be related to photoprotection rather than light‐harvesting, suggesting that these families may have originated as stress‐response proteins. In support of this, all members of the LHC superfamily bind significant amounts of carotenoid, and much of the variation between them resides in the bewildering array of different carotenoids they bind. In fact, it has been suggested that this family originated as carotenoid‐binding proteins and only later acquired Chl (Gantt, E. 1998; Photosynthesis: Mechanisms & Effects I, pp. 239‐246).