Overexpression of Glycolate Oxidase Confers Improved Photosynthesis under High Light and High Temperature in Rice.

Li-Li Cui,Yu-Sheng Lu,Xin-Xiang Peng,Chengwei Yang,Yong Li

doi:10.3389/fpls.2016.01165

Abstract

While glycolate oxidase (GLO) is well known as a key enzyme for the photorespiratory metabolism in plants, its physiological function and mechanism remains to be further clarified. Our previous studies have shown that suppression of GLO in rice leads to stunted growth and inhibited photosynthesis (Pn) which is positively and linearly correlated with decreased GLO activities. It is, therefore, of interest to further understand whether Pn can be improved when GLO is up-regulated? In this study, four independent overexpression rice lines, with gradient increases in GLO activity, were generated and functionally analyzed. Phenotypic observations showed that the growth could be improved when GLO activities were increased by 60 or 100%, whereas reduced growth was noticed when the activity was further increased by 150 or 210%. As compared with WT plants, all the overexpression plants exhibited significantly improved Pn under conditions of high light and high temperature, but not under normal conditions. In addition, the overexpression plants were more resistant to the MV-induced photooxidative stress. It was further demonstrated that the antioxidant enzymes, and the antioxidant metabolite glutathione was not significantly altered in the overexpression plants. In contrast, H2O2 and salicylic acid (SA) were correspondingly induced upon the GLO overexpression. Taken together, the results suggest that GLO may play an important role for plants to cope with high light and high temperature, and that H2O2 and SA may serve as signaling molecules to trigger stress defense responses but antioxidant reactions appear not to be involved in the defense.

Highlights

Photorespiration (PR) is the second highest metabolite flux only next to photosynthesis (Pn) in C3 plants, with flux rates amounting to 25–30% of Pn (Sharkey, 1988; Peterhansel and Maurino, 2011)
Since we have previously demonstrated that GLO1 and GLO4 were responsible for controlling glycolate oxidase (GLO)
The results found that the overexpression plants had significantly higher Pn than WT plants only under the high temperature plus high light conditions, but not different under only this high light (900 μmol m−2 s−1) (Figure 5A)

Summary

Introduction

Photorespiration (PR) is the second highest metabolite flux only next to photosynthesis (Pn) in C3 plants, with flux rates amounting to 25–30% of Pn (Sharkey, 1988; Peterhansel and Maurino, 2011). While different sources for H2O2 have been reported in plants, the peroxisomal H2O2 has recently received increasing attention and shown to play important roles in the programmed cell death (PCD) and biotic defense responses (Chaouch and Noctor, 2010; Sewelam et al, 2014). GLO was implicated in plant resistance to pathogens (Mukherjee and Choudhuri, 1983; Taler et al, 2004; Rojas et al, 2012; Gilbert and Wolpert, 2013). It is more recently demonstrated that GLO is an alternative source for the production of H2O2 during both gene-for-gene and non-host resistance in Nicotiana benthamiana and Arabidopsis (Rojas et al, 2012; Gilbert and Wolpert, 2013)

Methods

Results

Conclusion