Tuning high-light acclimation via Fd-driven PSI regulation: evidence for alternative electron flow?

Abstract

A tighter control of photosystem I (PSI) activity may redefine how plants partition electron flow between productive and protective pathways under fluctuating light. Plants must continuously adjust light energy use to sustain growth while preventing photodamage, making the regulation of thylakoid electron flow a central determinant of photosynthetic performance.

We previously generated transplastomic tobacco lines overexpressing pea ferredoxin (Fd1-OE; Blanco et al., 2013). Under greenhouse conditions (150 μmol photons m⁻² s⁻¹), these plants exhibited enhanced photoprotection (higher NPQ), but reduced growth and a variegated phenotype. To resolve this apparent trade-off, we exposed Fd1-OE plants to increasing growth irradiance (350–1400 μmol photons m⁻² s⁻¹). At the highest irradiance, the phenotype was largely reversed: Fd1-OE plants displayed improved photochemical efficiency, loss of variegation, and near wild-type growth. Notably, enhanced NPQ was maintained across all conditions.

OJIP analysis revealed improved PSI performance, further supported by an increased post-illumination fluorescence rise (PIFR), consistent with enhanced PSI activity. Together, these results indicate that elevated ferredoxin levels promote a refined coordination between electron transport and energy dissipation. We propose that Fd-driven modulation of PSI activity enables alternative electron flow pathways that optimize the balance between photochemistry and photoprotection across light regimes. This work highlights PSI remodeling as a promising target to improve plant acclimation and performance under fluctuating and high-light environments.

Publications

Blanco NE, Ceccoli RD, Via MV, Voss I, Segretin ME, Bravo-Almonacid FF, Melzer M, Hajirezaei MR, Scheibe R, Hanke GT. 2013. Expression of the minor isoform pea ferredoxin in tobacco alters photosynthetic electron partitioning and enhances cyclic electron flow. Plant Physiology 161(2): 866–879.

Brugnara C, Diaz MC, Bultri J, Liebsch D, Hita FJ, Lucero DA, Fusari CM, Dengjel J, Levi V, Blanco NE. 2026. Quantification of SnRK1.1 response through analysis of its intracellular distribution. Plant Cell Reports 45(2): 26.

Llorente B*, Segretin ME*, Giannini E, Lobais C, Juárez ME, Paulsen IT, Blanco NE*. 2021. Homecoming: rewinding the reductive evolution of the chloroplast genome for increasing crop yields. Nature Communications 12: 6734.

Yang Q, Blanco NE*, Hermida-Carrera C, Lehotai N, Hurry V, Strand A. 2020. Two dominant boreal conifers use contrasting mechanisms to reactivate photosynthesis in the spring. Nature Communications 11(1): 128.