Analysis of chlorophyll a fluorescence and proteomic differences of rice leaves in response to photooxidation

Abstract

This study investigated the effects of increased sunlight on photooxidation of rice leaf mutant 812HS and its wild-type 812S under field conditions. Light is important for plant growth and development. However, when the absorbed energy exceeds the capacity of utilization of photosynthesis, it leads to the accumulation of singlet oxygen molecules and other reactive oxygen species, which causes oxidative damage. Chlorophyll a fluorescence was applied to examine photosystem II photochemistry. The results demonstrated that intensive light had a negative influence on plant photosynthetic processes. However, the electron transport chain was inhibited and energy dissipation was increased, which can minimize photooxidative damage to the optical system. Meanwhile, proteomic analysis showed that the differential expression of proteins in response to photooxidation participated in multiple pathways, including ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) large subunit, RuBisCO large chain precursor, RuBisCO activase, flavodoxin-like quinone reductase 1, l-ascorbate peroxidase S, oxygen-evolving complex protein 1, and glycolate oxidase. The results indicated that photooxidation induced a response in the rice via the stress-related pathway. The aforementioned proteins, identified by two-dimensional gel electrophoresis (2-DE) and mass spectrometry (MS), may be very useful in comprehending how plants respond to photooxidation and can be used as characteristics of stress-induced signals. The results of chlorophyll fluorescence parameter analysis demonstrated the negative influence of intense light on plant photosynthetic processes. This was evidenced by the dissipation of excessive energy and the suppression of the electron transport chain to minimize photooxidative damage to the proteins. Future studies should compare the proteomic difference with parallel gene expression and metabolite profiles.