Centre of Excellence for Translational Photosynthesis, Division of Plant Science, Research School of Biology, The Australian National University, Acton, Australian Capital Territory, Australia.
School of Biological Sciences, Monash University, Melbourne, Victoria, Australia.
Physiol Plant. 2022 Nov;174(6):e13803. doi: 10.1111/ppl.13803.
Photosynthesis is fundamental for plant growth and yield. The cytochrome b 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 b f, the Rieske FeS protein, led to up to a 40% increase in the abundance of the complex in Nicotiana tabacum (tobacco) and was accompanied by an enhanced in vitro cytochrome f activity, indicating a full functionality of the complex. Analysis of transgenic plants overexpressing Rieske FeS by the light-induced fluorescence transients technique revealed a more oxidised primary quinone acceptor of photosystem II (Q ) 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 q , the energy-dependent component of nonphotochemical quenching, in transgenic plants suggests a more rapid buildup of the transmembrane proton gradient, also supporting the increased in vivo cytochrome b f activity. However, there was no consistent increase in steady-state rates of electron transport or CO 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 b f and may have the potential to increase plant productivity if combined with other traits.
光合作用是植物生长和产量的基础。细胞色素 b-f 复合物催化类囊体电子传递中的限速步骤，因此代表了光合作用调节的一个重要点。在这里，我们表明，细胞色素 b-f 的单个核心亚基，即 Rieske FeS 蛋白的过表达，导致烟草中细胞色素 b-f 复合物的丰度增加了高达 40%，并且体外细胞色素 f 活性增强，表明复合物具有完整的功能。通过光诱导荧光瞬变技术对过表达 Rieske FeS 的转基因植物进行分析表明，与对照植物相比，光系统 II（Q ）和质体醌库的初级醌受体更加氧化，并且在光照变化时，电子从质体醌库向光系统 I 的传递更快。在转基因植物中，q 的建立更快，q 是非光化学猝灭的能量依赖成分，这表明跨膜质子梯度的建立更快，这也支持细胞色素 b-f 的体内活性增加。然而，在实验室条件或田间试验中生长的过表达 Rieske FeS 的植物中，电子传递或 CO 同化的稳态速率并没有一致增加，这表明在光照变化时，复合物的体内活性只是短暂增加。我们的结果表明，在烟草中过表达 Rieske FeS 可以增加功能性细胞色素 b-f 的丰度，如果与其他性状结合，可能有潜力提高植物生产力。
