Proton Gradient Regulation 5 is required to avoid photosynthetic oscillations during light transitions
Gustaf E Degen1, Federica Pastorelli1, Matthew P Johnson1
1Plants, Photosynthesis & Soil, School of Biosciences, University of Sheffield, Sheffield, UK.
Journal of Experimental Botany
|October 27, 2023
Summary
The Proton Gradient Regulation 5 (PGR5) protein is crucial for photosynthesis regulation. Its deficiency in Arabidopsis plants leads to increased oscillations, impacting CO2 assimilation and highlighting PGR5
Area of Science:
- Plant Physiology
- Photosynthesis Research
- Molecular Biology
Background:
- Photosynthesis involves light reactions producing ATP and NADPH, consumed by the Calvin-Benson-Bassham (CBB) cycle.
- Environmental changes can disrupt ATP/NADPH balance, causing photo-oxidative stress and reduced CO2 assimilation.
- Such imbalances manifest as oscillations in physiological signals like chlorophyll fluorescence and CO2 uptake.
Purpose of the Study:
- To investigate the regulatory mechanisms plants use to suppress photosynthetic oscillations.
- To identify genetic factors contributing to altered oscillatory behavior under environmental stress.
Main Methods:
- Analysis of photosynthetic oscillations in wild-type Arabidopsis and mutant lines (pgr5, NADH-dehydrogenase-like CET mutants, hope2).
- Induction of oscillations via sudden shifts in CO2 concentration or light intensity.
- Measurement of chlorophyll fluorescence, P700, electrochromic shift, and CO2 uptake.
- Assessment of proton motive force and ATP synthesis rates.
Main Results:
- The Arabidopsis pgr5 mutant, lacking Proton Gradient Regulation 5 (PGR5)-dependent cyclic electron transfer (CET), showed significantly increased photosynthetic oscillations.
- Mutants deficient in NADH-dehydrogenase-like CET did not exhibit increased oscillations.
- The hope2 mutant also showed no oscillations, ruling out loss of photosynthetic control or high ATP synthase conductivity as causes.
- pgr5 mutants displayed slower proton motive force and ATP synthesis upon perturbation, leading to electron transfer chain reduction and oscillations.
Conclusions:
- PGR5-dependent cyclic electron transfer plays a critical role in stabilizing photosynthesis against environmental fluctuations.
- PGR5-mediated CET is essential for damping oscillations and preventing losses in CO2 fixation.
- Understanding PGR5 function provides insights into plant adaptation to environmental stress.
Keywords:
ATP synthaseCO2 fixationcyclic electron transferelectron transportoscillationphotosynthesisphotosynthetic controlMore Related Videos
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