Accumulation of geranylgeranylated chlorophylls in the pigment-protein complexes of Arabidopsis thaliana acclimated to green light: effects on the organization of light-harvesting complex II and photosystem II functions

Václav Karlický,Vladimír Špunda,Győző Garab,Michal Štroch,Jakub Nezval,Irena Kurasová,Zuzana Kmecová Materová

doi:10.1007/s11120-021-00827-1

Abstract

Light quality significantly influences plant metabolism, growth and development. Recently, we have demonstrated that leaves of barley and other plant species grown under monochromatic green light (500–590 nm) accumulated a large pool of chlorophyll a (Chl a) intermediates with incomplete hydrogenation of their phytyl chains. In this work, we studied accumulation of these geranylgeranylated Chls a and b in pigment-protein complexes (PPCs) of Arabidopsis plants acclimated to green light and their structural–functional consequences on the photosynthetic apparatus. We found that geranylgeranylated Chls are present in all major PPCs, although their presence was more pronounced in light-harvesting complex II (LHCII) and less prominent in supercomplexes of photosystem II (PSII). Accumulation of geranylgeranylated Chls hampered the formation of PSII and PSI super- and megacomplexes in the thylakoid membranes as well as their assembly into chiral macrodomains; it also lowered the temperature stability of the PPCs, especially that of LHCII trimers, which led to their monomerization and an anomaly in the photoprotective mechanism of non-photochemical quenching. Role of geranylgeranylated Chls in adverse effects on photosynthetic apparatus of plants acclimated to green light is discussed.

Highlights

Spectral quality of photosynthetic active radiation together with its intensity significantly influence plant metabolism, growth and development
We have demonstrated that leaves of barley and other plant species grown under monochromatic green light (GL) accumulated a large pool of geranylgeranyl-chlorophyll a (Chl a), Chl intermediates with incomplete hydrogenation of their phytyl chains (Materová et al 2017)
In order to reliably determine the effect of geranylgeranylated Chls a and b on the organization and stability of pigment-protein complexes (PPCs) in the thylakoid membrane, plant material containing a more pronounced amount of these Chls a and b was required than in our previous study on barley, in which maximally 15% geranylgeranylated Chl a and only trace amounts of Chl b accumulated in plants grown under green light from the seed for two weeks (Materová et al 2017)

Summary

Introduction

Spectral quality of photosynthetic active radiation together with its intensity significantly influence plant metabolism, growth and development. Green light is still associated with the misconception that it is only poorly absorbed by plant leaves in contrast to blue and red light. Photosynthesis Research (2021) 149:233–252 effect causing attenuation of strongly absorbed blue and red light, but only marginal decrease of weakly absorbing green light (Terashima et al 2009). With the development of light-emitting diodes (LEDs), providing single colors in the range from ultraviolet to infrared, LEDs have become an innovative light source for such systems (Ouzounis et al 2015; Bourget 2008) and simplified and boosted research on the effects of monochromatic light treatment (Landi et al 2020). In indoor agriculture the spectral characteristics of LED light sources are crucial for plant growth and quality via the regulation of photosynthesis, photomorphogenesis and secondary metabolism. Effects of single colors, including green, become more physiologically relevant (He et al 2019)

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