Environmental control of plant nuclear gene expression by chloroplast redox signals

Abstract

Plant photosynthesis takes place in specialized cell organelles, the chloroplasts, which perform all essential steps of this process. The proteins involved in photosynthesis are encoded by genes located on the plastid and nuclear genomes. Proper function and regulation of light harvesting and energy fixation thus requires a tight coordination of the gene expression machineries in the two genetic compartments. This is achieved by a bi-directional exchange of information between nucleus and plastids. Signals emerging from plastids report the functional and developmental state of the organelle to the nucleus and initiate distinct nuclear gene expression profiles, which trigger responses that support or improve plastid functions. Recent research indicated that this signaling is absolutely essential for plant growth and development. Reduction/oxidation (redox) signals from photosynthesis are key players in this information network since they do report functional disturbances in photosynthesis, the primary energy source of plants. Such disturbances are caused by environmental fluctuations for instance in illumination, temperature, or water availability. These environmental changes affect the linear electron flow of photosynthesis and result in changes of the redox state of the components involved [e.g., the plastoquinone (PQ) pool] or coupled to it (e.g., the thioredoxin pool). Thus, the changes in redox state directly reflect the environmental impact and serve as immediate plastidial signals to the nucleus. The triggered responses range from counterbalancing reactions within the physiological range up to severe stress responses including cell death. This review focuses on physiological redox signals from photosynthetic electron transport (PET), their relation to the environment, potential transduction pathways to the nucleus and their impact on nuclear gene expression.

Transcript level coordination of carbon pathways during silicon starvation‐induced lipid accumulation in the diatom Thalassiosira pseudonana

“…communicate with the nucleus to regulate nuclear transcription and integrate chloroplast and nonchloroplast metabolism (Rüdiger & Oster, 2012; Rochaix & Ramundo, 2014). Reduced PET as a result of damage to PSII detected at 8 h of silicon starvation could result in an overall shift in the redox state of the chloroplast (Pfalz et al ., 2012). P ‐ I parameters α and P max also decreased at 8 h, from a limit in the supply of ATP and NADPH from impaired PET, a reduction in the supply of intermediates required for carbon fixation, and/or an increase in oxygen fixation by RuBisCO.…”

Chlorophyll b degradation by chlorophyll b reductase under high-light conditions

“…The mechanism for the reduction in the CP1 level in cbr mutants is still unresolved in this study. One potential mechanism is that the CP1 levels are decreased to balance excitation between PSI and PSII (Pfalz et al 2012). In cbr plants, PSII is damaged and the plastoquinone pool must be oxidized.…”

The Regulation of Photosynthetic Structure and Function during Nitrogen Deprivation in Chlamydomonas reinhardtii

“…Another significant posttranslational change is the relative partitioning of light-harvesting complexes between the photosystems, which occurs within 6 h, before the levels of the antennae proteins have changed significantly. Posttranslational regulation of photosynthesis is known to be important in a range of stress responses as well as in diurnal changes (de Vitry et al, 1989;Geiger and Servaites, 1994;Turkina et al, 2006;Pfalz et al, 2012). Such changes include structural modifications of individual proteins and photosynthetic complexes as well as allosteric regulation of enzyme activities.…”