Faster responses of photosynthesis to light transitions increase biomass and grain yield in transgenicSorghum bicoloroverexpressing Rieske FeS

Abstract

AbstractSorghum is one of the most important crops providing food and feed in many of the world’s harsher environments. Sorghum utilises the C4pathway of photosynthesis in which a biochemical carbon concentrating mechanism results in high CO2assimilation rates. Overexpressing the Rieske subunit of the Cytochromeb6fcomplex was previously shown to increase the rate of photosynthetic electron transport and stimulate CO2assimilation in the model C4plantSetaria viridis. To test whether productivity of C4crops could be improved by Rieske overexpression, we created transgenicSorghum bicolorplants with increased Rieske content. The transgenic plants showed no marked changes in abundance of other photosynthetic proteins or chlorophyll content. Increases in yield of Photosystem II and CO2assimilation rate as well as faster responses of non-photochemical quenching during transient photosynthetic responses were observed as a result of an elevatedin vivoCytochromeb6factivity in plants overexpressing Rieske. The steady-state rates of electron transport and CO2assimilation did not differ between transgenic and control plants, suggesting that Cytochromeb6fis not the only factor limiting electron transport in sorghum at high light and high CO2. Nevertheless, more agile responses of photosynthesis to light transitions led to increases in biomass and grain yield in plants overexpressing Rieske. Our results indicate that increasing Rieske content could boost productivity of C4crops by improving the efficiency of light utilisation and conversion to biomass.