Augmenting light coverage for photosynthesis through YFP-enhanced charge separation at the Rhodobacter sphaeroides reaction centre

Katie J Grayson,Christine Kirmaier,Preston Dilbeck,Kaitlyn M Faries,Dariusz M Niedzwiedzki,Andrew Hitchcock,Xia Huang,Dewey Holten,Pu Qian,Graham J Leggett,Cvetelin Vasilev,Jonathan M Yuen,C Neil Hunter,Elizabeth C Martin

doi:10.1038/ncomms13972

Abstract

Photosynthesis uses a limited range of the solar spectrum, so enhancing spectral coverage could improve the efficiency of light capture. Here, we show that a hybrid reaction centre (RC)/yellow fluorescent protein (YFP) complex accelerates photosynthetic growth in the bacterium Rhodobacter sphaeroides. The structure of the RC/YFP-light-harvesting 1 (LH1) complex shows the position of YFP attachment to the RC-H subunit, on the cytoplasmic side of the RC complex. Fluorescence lifetime microscopy of whole cells and ultrafast transient absorption spectroscopy of purified RC/YFP complexes show that the YFP–RC intermolecular distance and spectral overlap between the emission of YFP and the visible-region (QX) absorption bands of the RC allow energy transfer via a Förster mechanism, with an efficiency of 40±10%. This proof-of-principle study demonstrates the feasibility of increasing spectral coverage for harvesting light using non-native genetically-encoded light-absorbers, thereby augmenting energy transfer and trapping in photosynthesis.

Highlights

Photosynthesis uses a limited range of the solar spectrum, so enhancing spectral coverage could improve the efficiency of light capture
The 525 nm emission maximum of SYFP2 has some overlap with the visible-region (QX) absorption band of bacteriochlorophyll a (BChl a) in the Rba. sphaeroides light-harvesting 1 (LH1) and reaction centre (RC) complexes, and the results of this study suggest that some of the energy absorbed by YFP migrates to the RC
The DcrtB mutation eradicates LH2 assembly[23,24] but does not affect the synthesis of the PufX polypeptide, which forms a portal for quinone traffic[16,25]

Summary

Introduction

Photosynthesis uses a limited range of the solar spectrum, so enhancing spectral coverage could improve the efficiency of light capture. Fluorescence lifetime microscopy of whole cells and ultrafast transient absorption spectroscopy of purified RC/YFP complexes show that the YFP–RC intermolecular distance and spectral overlap between the emission of YFP and the visible-region (QX) absorption bands of the RC allow energy transfer via a Forster mechanism, with an efficiency of 40±10%. This proof-of-principle study demonstrates the feasibility of increasing spectral coverage for harvesting light using non-native genetically-encoded light-absorbers, thereby augmenting energy transfer and trapping in photosynthesis. This work forms the basis of future studies involving the creation of novel, tailored light-harvesting antenna complexes for increased spectral coverage of in vivo photosynthesis

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Results

Conclusion