Research Article

Light-dependent chlorophyll f synthase is a highly divergent paralog of PsbA of photosystem II

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Science  07 Jul 2016:
DOI: 10.1126/science.aaf9178

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Chlorophyll (Chl) f permits some cyanobacteria to expand the spectral range for photosynthesis by absorbing far-red light. We used reverse genetics and heterologous expression to identify the enzyme for Chl f synthesis. Null mutants of “super-rogue” psbA4 genes, divergent paralogs of psbA genes encoding the D1 core subunit of Photosystem II, abolished Chl f synthesis in two cyanobacteria that grow in far-red light. Heterologous expression of the psbA4 gene, which we rename chlF, enables Chl f biosynthesis in Synechococcus sp. PCC 7002. Because the reaction requires light, Chl f synthase is probably a photo-oxidoreductase that employs catalytically useful Chl a molecules, tyrosine YZ, and plastoquinone like photosystem II but lacks a Mn4Ca1O5 cluster. Introduction of Chl f biosynthesis into crop plants could expand their solar energy utilization.

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