Maize GOLDEN2-LIKE genes enhance biomass and grain yields in rice by improving photosynthesis and reducing photoinhibition

Xia Li,Peng Wang,Jing Li,Ming Zhao,Jane A Langdale,Wenbin Zhou,Shaobo Wei,Jun Yang,Yanyan Yan

doi:10.1038/s42003-020-0887-3

Abstract

Photosynthetic efficiency is a major target for improvement of crop yield potential under agricultural field conditions. Inefficiencies can occur in many steps of the photosynthetic process, from chloroplast biogenesis to functioning of the light harvesting and carbon fixation reactions. Nuclear-encoded GOLDEN2-LIKE (GLK) transcription factors regulate some of the earliest steps by activating target genes encoding chloroplast-localized and photosynthesis-related proteins. Here we show that constitutive expression of maize GLK genes in rice leads to enhanced levels of chlorophylls and pigment-protein antenna complexes, and that these increases lead to improved light harvesting efficiency via photosystem II in field-grown plants. Increased levels of xanthophylls further buffer the negative effects of photoinhibition under high or fluctuating light conditions by facilitating greater dissipation of excess absorbed energy as heat. Significantly, the enhanced photosynthetic capacity of field-grown transgenic plants resulted in increased carbohydrate levels and a 30–40% increase in both vegetative biomass and grain yield.

Highlights

Photosynthetic efficiency is a major target for improvement of crop yield potential under agricultural field conditions
Figure 2k shows that D1 protein levels were higher in the transgenic lines than wild type (WT), both before and after 4-h high light treatment, in both the presence and absence of lincomycin. Together these results suggest that the resistance to photooxidative damage observed in transgenic lines expressing ZmGLK1 or ZmG2 is provided by elevated levels of photosystem II (PSII) proteins
We have shown that constitutive expression of ZmGLK1 or ZmG2 in rice leads to elevated levels of Chl, carotenoid, and xanthophyll cycle pigments and to increased levels of some PSII components (Figs. 1 and 3)

Summary

Introduction

Photosynthetic efficiency is a major target for improvement of crop yield potential under agricultural field conditions. Plants have to protect themselves from light damage either through dissipation of excess light energy captured by the light-harvesting antennae of PSII (LHCII) as heat, a process termed non-photochemical quenching (NPQ)[7], or through operation of a repair cycle that restores PSII structure, restoration of degraded D1 protein[8] Both non-photochemical and photochemical reactions are being targeted to improve photosynthetic efficiency in field-grown crops. Increased levels of Rieske FeS protein resulted in increased electron transport rates, biomass, and seed yield in Arabidopsis[17], and engineered SBPase activity improved photosynthetic CO2 assimilation, grain and biomass yield in wheat and tobacco[18,19] These examples, plus those outlined for NPQ, demonstrate that the manipulation of individual steps in nonphotochemical or photochemical processes can improve photosynthetic efficiency, but the coordinated manipulation of multiple steps has not been well demonstrated in the field

Methods

Results

Conclusion