Biology subjects

Crepin, A.

Publications and source records attributed to Crepin, A..

3 recordsLinked to original sources

bioRxiv2026

Sustained photoprotection involves enhanced fluorescence intermittency in a subpopulation of LHCII

Photoprotection against excess energy is essential for the survival of photosynthetic organisms under adverse conditions. In plants, excess energy can be dissipated as heat through non-photochemical quenching (NPQ) of chlorophyll fluorescence, involving the trimeric light-harvesting complex II (LHCII), the major antenna of photosystem II. How NPQ affects antenna proteins remains debated, especially as most studies focus on short-lived components artificially induced in vitro. Here, we characterize the effects of qH, a long-lived NPQ component, on the fluorescence properties of natively quenched LHCII. Single-molecule fluorescence measurements, combined with biochemical and biophysical ensemble approaches, reveal a larger and more quenched subpopulation of LHCII trimers exhibiting fluorescence intermittency in samples with qH compared to those without. This behavior is linked to a small conformational change that stabilizes a quenched state, enhancing photoprotection at the antenna level. These findings provide new insights into sustained NPQ and its role in regulating energy dissipation under natural light conditions.

plant biology↗

bioRxiv2025

Guanosine tetraphosphate (ppGpp) signalling promotes high-light tolerance in Arabidopsis thaliana.

Guanosine tetraphosphate (ppGpp) is a hyperphosphorylated nucleotide originally discovered in prokaryotes and found in the chloroplasts of plants and algae. In plants, ppGpp signalling plays a role as a regulator of photosynthetic activity, which is important in acclimation to environmental stresses such as nitrogen limitation. However, the full range of stresses involving ppGpp signalling is not yet known. Here, we investigated the role of ppGpp accumulation in the acclimation of plants to high light. We found that the over-accumulation of ppGpp in transgenic lines that overexpress RSH3 (OX:RSH3) increases tolerance to high light intensity. Although ppGpp leads to higher non-photochemical energy dissipation (NPQ) than in wild-type plants, we show that NPQ is not critical for the enhanced high-light tolerance. Rather, our results show that ppGpp accumulation leads to broad changes in plant physiology that prime plants to resist and subsequently recover from high light exposure. ppGpp levels themselves also increase in response to high light exposure, suggesting that ppGpp signalling may play a physiological role in high light acclimation. Our work highlights the importance of ppGpp signalling in plant stress acclimation.

plant biology↗

bioRxiv2025

The minor antennae of photosystem II contribute to qH-energy dissipation in Arabidopsis

Photosynthesis is a biological process that converts light energy into chemical energy. Excessive light can damage the photosynthetic machinery, so plants have evolved photoprotective mechanisms such as non-photochemical quenching (NPQ). Among the NPQ mechanisms, qH is a form of sustained quenching, dependent on LIPOCALIN IN THE PLASTID (LCNP) and repressed by SUPPRESSOR OF QUENCHING 1 (SOQ1), protecting against abiotic stress. Recently, we showed in Arabidopsis thaliana that qH can occur in the major light-harvesting complexes (Lhcb1, Lhcb2, Lhcb3) but independently of any specific major antenna. Interestingly, in mutants with little or no accumulation of major antennae (koLHCII, lhcb1, cpsrp43), qH can still be induced. Here, we show that the minor antennae can be quenched by qH and remain quenched once isolated. To investigate the role of minor antennae in qH, we combined the soq1 mutant, which displays high qH, with mutations in each minor antenna type (Lhcb4, Lhcb5, or Lhcb6), or with a mutant lacking all minor antennae. None are strictly required for qH to occur. Still, the absence of Lhcb6 decreases qH induction likely due to an indirect effect from the slower electron transport rate and/or a different macro-organization of photosynthetic complexes in the thylakoids. Overall, this work demonstrates that the minor antennae are a secondary target for qH and could serve as an additional safety valve for photoprotective energy dissipation during prolonged stress.

plant biology↗