PROTECTIVE ROLES OF D1 PROTEIN TURNOVER AND THE XANTHOPHYLL CYCLE IN TOMATO (SOLANUM LYCOPERSICUM) UNDER SUB-HIGH TEMPERATURE AND HIGH LIGHT STRESS

Tao Lu ,Mingfang Qi ,Yufeng Liu ,Jiazhi Lu ,Zenghui Sun ,Tianlai Li

doi:10.15302/j-fase-2021383

Abstract

<List> <ListItem><ItemContent> • D1 turnover plays a more important role than xanthophyll cycle in photoprotection under sub-high temperature and high light (HH) conditions in tomato. </ItemContent></ListItem> <ListItem><ItemContent> • D1 protein turnover and xanthophyll cycle avoided the accumulation of excess energy and photooxidative damage of photosystem through maintaining photosynthetic pigments content and inducing changes in NPQ core components. </ItemContent></ListItem> <ListItem><ItemContent> • D1 protein turnover and xanthophyll cycle can also avoided accumulation of ROS and membrane lipid peroxidation by maintaining the activity of the ROS scavenging system. </ItemContent></ListItem></List> D1 protein turnover and the xanthophyll cycle (XC) are important photoprotective mechanisms in plants that operate under adverse conditions. Here, streptomycin sulfate (SM) and dithiothreitol (DTT) were used in tomato plants as inhibitors of D1 protein turnover and XC to elucidate their photoprotective impacts under sub-high temperature and high light conditions (HH, 35°C, 1000 µmol·m-2·s-1). SM and DTT treatments significantly reduced the net photosynthetic rate, apparent quantum efficiency, maximum photochemical efficiency, and potential activity of photosystem II, leading to photoinhibition and a decline in plant biomass under HH. The increase in reactive oxygen species levels resulted in thylakoid membrane lipid peroxidation. In addition, there were increased non-photochemical quenching and decreased chlorophyll pigments in SM and DTT application, causing an inhibition of D1 protein production at both transcriptional and translational levels. Overall, inhibition of D1 turnover caused greater photoinhibition than XC inhibition. Additionally, the recovery levels of most photosynthesis indicators in DTT-treated plants were higher than in SM-treated plants. These findings support the view that D1 turnover has a more important role than XC in photoprotection in tomato under HH conditions.

Highlights

A severe consequence of climate change is global warming with heat waves usually accompanied by high light intensity occurring globally, including many important agricultural production areas
We studied the photosynthetic properties of tomato to elucidate the possible protective effects of D1 turnover and xanthophyll cycle (XC) on photosystem II (PSII)
Y(NPQ) and Y(NO) increased significantly under high light stress (HH) compared with H2O-treated plants, Y(NPQ) and Y(NO) of SM group were significantly higher, but no significant differences in Y(NO) were found between H2O- and DTT-treated plants

Summary

Introduction

A severe consequence of climate change is global warming with heat waves usually accompanied by high light intensity occurring globally, including many important agricultural production areas. When the solar energy absorbed by plants exceeds their capacity, generation of excess energy disturbs several physiologic processes in the cells, including the destruction of antenna systems, oxygen evolving complex and reaction centers, as well as the denaturation of plant proteins. These result in photoinhibition or photodamage of photosystems[1]. Previous studies have shown that moderately high temperatures and strong light can enhance the tolerance of plants to photoinhibition, but high-intensity high temperatures as well as strong light can restrict the ability of plants to assimilate photosynthetic carbon by stomatal or non-stomatal factors[2] It is well-established that photosystem II (PSII) is the primary site of photosynthetic activity, which can be destroyed by strong light and high temperatures[3]. Despite the conserved nature of PSII vulnerability, the actual photodamage mechanism varies from one crop to another, with the main discrepancy being whether photodamage is caused by the donor or acceptor side of the PSII reaction center[4]

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