Responses of the Photosynthetic Electron Transport Reactions Stimulate the Oxidation of the Reaction Center Chlorophyll of Photosystem I, P700, under Drought and High Temperatures in Rice.

Shinya Wada,Chikahiro Miyake,Yuji Suzuki,Daisuke Takagi,Amane Makino

doi:10.3390/ijms20092068

Shinya Wada, Chikahiro Miyake + Show 3 more

Open Access

https://doi.org/10.3390/ijms20092068

Copy DOI

Abstract

It is of interest how photosynthetic electron transport (PET) reactions respond to excess light energy caused by the combination of drought stress and high temperatures. Since such information is scarcely available for photosystem I (PSI), this question was explored in rice (Oryza sativa L.) plants subjected to drought stress, using culture solutions that contain poly(ethylene glycol) at different concentrations under two day/night temperature regimes. At 27/22 °C (day/night), drought stress led to the oxidation of the reaction center of the chlorophyll of PSI (P700), and also led to decreases in the quantum efficiencies of photosystem II (PSII) and PSI, and a reduction of the primary quinone electron acceptor of PSI. Such drought stress responses were wholly stimulated at 35/30 °C. These parameters were strongly correlated with each other and were minimally affected by temperature. These results indicate that the drought stress responses of the respective PET reactions are closely associated with each other in the oxidization of P700 and that such responses are stimulated at high temperatures. The underlying mechanisms of these phenomena were discussed. While P700 oxidation is thought to suppress reactive oxygen species (ROS) production, PSI photoinhibition was observed under severe stress conditions, implying that P700 oxidation is not sufficient for the protection of PSI under drought stress.

Highlights

Drought is one of the most serious abiotic stresses experienced by plants and is often accompanied by high temperatures
When plants underwent drought stress, P700 oxidation was reported to be enhanced concomitantly with decreases in the quantum efficiency of photosystem II (PSII) [Y(II)], which in turn were accompanied by increases in non-photochemical quenching (NPQ), a reduction of the plastoquinone pool, and decreases in the quantum efficiency of photosystem I (PSI) [Y(I)] [1,18,20,21,22,34,35,36]. These results suggest that the photosynthetic electron transport (PET) reactions, upstream of PSI, cooperatively respond to drought stress in order to protect P700 from over-reduction
These results show that considerable PSII photoinhibition occurred only when plants were subjected to severe drought stress at high temperatures

Summary

Introduction

Drought is one of the most serious abiotic stresses experienced by plants and is often accompanied by high temperatures. How the photosynthetic machinery responds to these stress conditions is of interest, as such information would be important for understanding and improving the stress tolerance of plants. Drought stress can lead to the generation of reactive oxygen species (ROS), which impair photosynthetic machinery. Stomatal closure in response to drought stress prevents water loss via transpiration but yields excess light energy, as decreases in CO2 availability within the leaves lead to decreases in energy consumption by the Calvin-Benson cycle [1]. Excess light energy can over-reduce the photosynthetic electron transport (PET) chain and lead to the generation of ROS [2,3].

Methods

Results

Conclusion