Journal Article

Chlorophyll–carotenoid excitation energy transfer and charge transfer in Nannochloropsis oceanica for the regulation of photosynthesis

Lyska, Dagmar, Iwai, Masakazu, Niyogi, Krishna K., Fischer, Alexandra L., Fleming, Graham R., Park, Soomin, Steen, Collin J., Endelman, Benjamin

2019

Overview

Nonphotochemical quenching (NPQ) is a proxy for photoprotective thermal dissipation processes that regulate photosynthetic light harvesting. The identification of NPQ mechanisms and their molecular or physiological triggering factors under in vivo conditions is a matter of controversy. Here, to investigate chlorophyll (Chl)–zeaxanthin (Zea) excitation energy transfer (EET) and charge transfer (CT) as possible NPQ mechanisms, we performed transient absorption (TA) spectroscopy on live cells of the microalga Nannochloropsis oceanica. We obtained evidence for the operation of both EET and CT quenching by observing spectral features associated with the Zea S₁ and Zea●+ excited-state absorption (ESA) signals, respectively, after Chl excitation. Knockout mutants for genes encoding either violaxanthin deepoxidase or LHCX1 proteins exhibited strongly inhibited NPQ capabilities and lacked detectable Zea S₁ and Zea●+ ESA signals in vivo, which strongly suggests that the accumulation of Zea and active LHCX1 is essential for both EET and CT quenching in N. oceanica.

• Publisher: National Academy of Sciences,National Academy of Sciences, Washington, DC (United States)
• Subject: Absorption / BASIC BIOLOGICAL SCIENCES / Biological Sciences / Biophysics and Computational Biology / Carotenoids - genetics / Carotenoids - metabolism / Charge transfer / Chlorophyll / Chlorophyll - chemistry / Chlorophyll - genetics / Chlorophyll - metabolism / Energy charge / Energy transfer / Energy Transfer - genetics / Excitation / excitation energy / In vivo methods and tests / Light / Light-Harvesting Protein Complexes - chemistry / Light-Harvesting Protein Complexes - metabolism / Microalgae - chemistry / Microalgae - genetics / Microalgae - metabolism / Nannochloropsis / Nannochloropsis oceanica / nonphotochemical quenching / Photosynthesis / Photosynthesis - genetics / Photosystem II Protein Complex - chemistry / Photosystem II Protein Complex - genetics / Photosystem II Protein Complex - metabolism / Physical Sciences / Physiological effects / Plant Biology / Proteins / Quenching / Spectroscopy / transfer / Violaxanthin / Violaxanthin de-epoxidase / Xanthophylls - chemistry / Xanthophylls - genetics / Xanthophylls - metabolism / Zeaxanthin / Zeaxanthins - chemistry / Zeaxanthins - genetics / Zeaxanthins - metabolism