Effect of glutathione reductase on photosystem II characterization and reactive oxygen species metabolism in cotton cytoplasmic male sterile line Jin A

Glutathione reductase (GR) maintains the cellular redox state by reducing oxidized glutathione to glutathione (GSH), which regulates antioxidant defense. Additionally, GR plays an essential role in photosynthesis; however, the mechanism by which GR regulates photosystem II (PSII) is largely unknown. We identified six, three, and three GR genes in Gossypium hirsutum, Gossypium arboreum, and Gossypium raimondii, respectively. We found that GhGR1 and GhGR3 proteins were localized in the chloroplasts, whereas GhGR5 was localized in the cell membrane. Cytoplasmic male sterile (CMS) line Jin A was ideal to explore GR functions because accumulation of reactive oxygen species (ROS) was increased and expression of GhGR was downregulated at the key stage of microspore abortion in anthers compared to maintainer Jin B. The GR activity and relative GhGR1, GhGR3, GhGR5 gene expressions decreased significantly at the key stage of microspore abortion in Jin A-CMS compared to that in Jin B, resulting in an increase in ROS and a decrease in photochemical efficiency in PSII. GhGR1 and GhGR3 overexpression in Arabidopsis decreased ROS levels in anthers and leaves compared to the wild-type. Biochemical analysis of GhGR1 and GhGR3 silencing in Gossypium L. showed that ROS content was increased and photochemical efficiency of PSII was inhibited in leaves. Complementation experiments in tobacco and yeast indicated that GhGR1 interacted with GhPsbX, which was one of the subunits of the PSII protein complex. Taken together, these findings suggest that chloroplast GR plays an important role in PSII and ROS metabolism by interacting with PsbX in cotton plants.