Accelerated Relaxation of Photoprotection Impairs Growth and Biomass Accumulation in Rice

Non-photochemical quenching (NPQ) is a vital photoprotective mechanism in plants, facilitating the dissipation of excess excitation energy as heat within photosystem II. Combined over expression photoprotection proteins, violaxanthin de-epoxidase (VDE), photosystem II subunit S protein (PsbS) and zeaxanthin epoxidase (ZEP) can accelerate the dynamics of photoprotection during the transition of leaves from sun to shade. However, not all transgenic plants exhibited increased efficiency of dynamic photosynthesis and growth performance in previous studies. To investigate the impact of Arabidopsis VDE, PsbS and ZEP genes (VPZ) on rice, we generated rice transgenic plants. The VPZ lines showed comparable NPQ induction and relaxation rate to those reported in previous studies, enhancing their photoprotective capacity. Nevertheless, they exhibit growth retardation, decreased photosynthetic capacity and reduced biomass accumulation under different light regimes and field conditions. This negative impact on the VPZ rice lines may be caused by the alterations to photochemical quenching under normal light conditions. Alleviating or eliminating the potential factor might help to enhance the growth and biomass accumulation in the VPZ lines.