Redox and light signals in the partitioning of photosynthetic electrons

Abstract

The light‐driven electron transport reactions of photosynthesis convert the free energy of sunlight into usable chemical energy. Plants contain two primary electron transport pathways: the linear electron transport from water to NADP+, producing NADPH and ATP, and the cyclic electron flow around photosystem I, generating just ATP. Recent research from our laboratory reveals that the sensory and gene regulatory function of a Chloroplast Sensor Kinase (CSK) is central to the partitioning of electrons into the linear and cyclic pathways. A conserved iron‐sulfur cluster enables CSK to sense the redox state of the electron carrier plastoquinone. CSK thus places the expression of multiple chloroplast genes under the regulatory control of plastoquinone. Through the phytochrome photoreceptor, light provides a further fail‐safe input into chloroplast gene regulation. The combined action of redox and light signals brings about stoichiometric changes in electron transport complexes with important implications for the flow of photosynthetic electrons.Support or Funding InformationPurdue University, Showalter Trust, and AgSEEDThe CSK‐based genetic switch in chloroplastsFigure 1