Biology subjects

de Vitry, C.

Publications and source records attributed to de Vitry, C..

3 recordsLinked to original sources

bioRxiv2023

Characterization of Tryptophan Oxidation Affecting D1 Degradation by FtsH in the Photosystem II Quality Control of Chloroplasts

Photosynthesis is one of the most important reactions for sustaining our environment. Photosystem II (PSII) is the initial site of photosynthetic electron transfer by water oxidation. Light in excess, however, causes the simultaneous production of reactive oxygen species (ROS), leading to photo-oxidative damage in PSII. To maintain photosynthetic activity, the PSII reaction center protein D1, which is the primary target of unavoidable photo-oxidative damage, is efficiently degraded by FtsH protease. In PSII subunits, photo-oxidative modifications of several amino acids such as Trp have been indeed documented, whereas the linkage between such modifications and D1 degradation remains elusive. Here, we show that an oxidative post-translational modification of Trp residue at the N-terminal tail of D1 is correlated with D1 degradation by FtsH during high-light stress. We revealed that Arabidopsis mutant lacking FtsH2 had increased levels of oxidative Trp residues in D1, among which an N-terminal Trp-14 was distinctively localized in the stromal side. Further characterization of Trp-14 using chloroplast transformation in Chlamydomonas indicated that substitution of D1 Trp-14 to Phe, mimicking Trp oxidation enhanced FtsH-mediated D1 degradation under high light, although the substitution did not affect protein stability and PSII activity. Molecular dynamics simulation of PSII implies that both Trp-14 oxidation and Phe substitution cause fluctuation of D1 N-terminal tail. Furthermore, Trp-14 to Phe modification appeared to have an additive effect in the interaction between FtsH and PSII core in vivo. Together, our results suggest that the Trp oxidation at its N-terminus of D1 may be one of the key oxidations in the PSII repair, leading to processive degradation by FtsH. Competing Interest StatementThe authors have no conflict of interest, financial or otherwise, in relation to this study Impact StatementOxidative modification of Tryptophan residues in the reaction center protein D1 may be a key to drive the Photosystem II repair, likely enhancing accessibility of FtsH protease to D1.

plant biology↗

bioRxiv2022

FtsH Protease Inactivation Allows Accumulation of Aberrant Photosystem II in a Chlamydomonas Rubredoxin Mutant

The assembly of photosystem II (PSII) requires the participation of assembly proteins that facilitate the step-wise association of its protein and pigment components into a functional complex capable of oxidizing water and reducing plastoquinone. We previously identified one such factor, the membrane-bound rubredoxin RBD1, but its precise role remains unknown in part due to the inability of the 2pac mutant strain of Chlamydomonas reinhardtii, which lacks RBD1, to accumulate PSII. Here, we show that decreased PSII accumulation in 2pac is due to increased proteolytic degradation. Inactivating the thylakoid membrane FtsH protease in the 2pac mutant background led to an increase in the abundance of PSII subunits and their integration into higher molecular weight complexes, including PSII dimers, capable of sustaining photoautotrophic growth. Dark- and low light-grown 2pac ftsh1-1 both accumulated a 23-kD fragment of the D1 protein, a marker typically associated with structural changes resulting from photodamage or photoinhibition. We introduced a HIS-tagged version of the PsbH protein into the 2pac ftsh1-1 background to purify and examine PSII. We found no detectable changes with respect to cofactor composition relative to the wild-type, leading to us to propose a model in which RBD1 promotes the proper folding of D1, possibly via delivery or reduction of the non-heme iron during PSII assembly. Our results demonstrate that introduction of the ftsh1-1 mutation into mutants defective in the biogenesis of thylakoid membrane complexes can allow for the accumulation and study of aberrant complexes that would otherwise be degraded due to their high protease sensitivity.

plant biology↗

bioRxiv2021

The rise and fall of the photoinhibition-related energy dissipation qI

Photosynthesis converts sunlight into chemical energy, sustaining the vast majority of the biosphere. Photosystem II (PSII), the oxygen-forming enzyme that initiates photosynthesis, is however particularly prone to light-induced damage in a process known as photoinhibition, which limits the productivity of both aquatic and land photosynthesis. Photoinhibition is associated with an energy dissipation process of unknown origin, termed qI. Here, we present a detailed biophysical and biochemical in vivo study of qI in model green alga Chlamydomonas reinhardtii. Time-resolved fluorescence measurements demonstrate the origin of qI, and indicate the PSII reaction centre as the site of the quencher. Oxygen-dependence of quenching site formation, but not photoinhibition itself, is shown, suggesting that two types of PSII damage - donor and acceptor-side impairment - can be separated. We then demonstrate that the quenching loss takes place in the absence of PSII repair, and is mediated by the degradation of photoinhibited PSII cores by the FtsH protease. Finally, we integrate data ranging from picoseconds to hours in the context of structure-function excitation energy-transferring membrane patches, revealing the extent of PSII heterogeneity from the onset of photoinhibition until the breakdown of damaged PSII. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=106 SRC="FIGDIR/small/434601v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@d7c64dorg.highwire.dtl.DTLVardef@1c2943org.highwire.dtl.DTLVardef@d90b83org.highwire.dtl.DTLVardef@182cd12_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIUpon photoinhibition, oxygen sensitization results in an irreversible formation of quenching (qI) and inactivation of Photosystem II C_LIO_LIqI takes place in the PSII reaction centre C_LIO_LIPhotoinhibition-induced D1 cleavage is much slower than qI formation C_LIO_LIFtsH metalloprotease is required to degrade quenching PSII reaction centres C_LIO_LIA multiscale energy transfer model describes heterogeneity of PSII during photoinhibition C_LI

plant biology↗