Rieske FeS overexpression in tobacco provides increased abundance and activity of Cytochrome b₆f

Photosynthesis is fundamental for plant growth and yield. The Cytochrome b₆ f complex catalyses a rate-limiting step in thylakoid electron transport and therefore represents an important point of regulation of photosynthesis. Here we show that overexpression of a single core subunit of Cytochrome bA ) and plastoquinone pool and faster electron transport from the plastoquinone pool to Photosystem I upon changes in irradiance, compared to control plants. A faster establishment of qE , the energy-dependent component of non-photochemical quenching, in transgenic plants suggests a more rapid build-up of the transmembrane proton gradient, also supporting the increased in vivo Cytochrome b₆ f activity. However, there was no consistent increase in steady-state rates of electron transport or CO₂ assimilation in plants overexpressing Rieske FeS grown in either laboratory conditions or field trials, suggesting that the in vivo activity of the complex was only transiently increased upon changes in irradiance. Our results show that overexpression of Rieske FeS in tobacco enhances the abundance of functional Cytochrome b₆ f and may have the potential to increase plant productivity if combined with other traits