Biology subjects

Traverso, E.

Publications and source records attributed to Traverso, E..

6 recordsLinked to original sources

bioRxiv2026

VIA1 is a conserved regulator of thylakoid membrane integrity that acts through VIPP1

Thylakoid membranes are indispensable for oxygenic photosynthesis, yet the mechanisms that protect these membranes from photooxidative damage remain poorly understood. By screening previously uncharacterized proteins induced during the chloroplast unfolded protein response, we identify VIA1 as an essential factor for preserving thylakoid integrity under high light in the model green alga Chlamydomonas reinhardtii. Loss of VIA1 causes hypersensitivity to photo-oxidative stress and rapid thylakoid swelling. VIA1 localizes to thylakoid membranes and directly binds Vesicle-Inducing Protein in Plastids 1 (VIPP1), an ESCRT-III-like protein essential for thylakoid biogenesis and remodeling. Structure-guided mutagenesis shows that this interaction is required for VIA1 function and is mediated by a winged-helix domain interface reminiscent of ESCRT-II/ESCRT-III binding mode. VIA1 orthologs from cyanobacteria and land plants rescue the Chlamydomonas via1 mutant phenotype, and disruption of VIA1 in Synechocystis sp. PCC 6803 impairs growth, especially under light stress. Together, these findings establish VIA1 as an evolutionarily conserved protein that contributes to thylakoid membrane homeostasis via its interaction with VIPP1. Significance StatementFrom cyanobacteria to land plants, all organisms performing oxygenic photosynthesis rely on thylakoid membranes to capture light and and produce oxygen. Yet these membranes are highly susceptible to environmental stress, particularly excess light, which causes oxidative damage to membrane lipids and proteins. How thylakoid integrity is maintained under these conditions remains a key open question. Here we identify VIA1 as a conserved factor required for maintaining thylakoid membrane structure under high light. VIA1 interacts with VIPP1, an ESCRT-III-like protein essential for thylakoid biogenesis, through a functionally indispensable interface reminiscent of ESCRT-II/ESCRT-III binding mode. The conservation of the VIA1-VIPP1 module across photosynthetic prokaryotes and eukaryotes suggests it arose early in the evolution of oxygenic photosynthesis and has been maintained ever since.

cell biology↗

bioRxiv2025

Harnessing photosynthetic ATP for whole-cell biocatalysis in the cyanobacterium Synechocystis

Photosynthetic organisms use sunlight to produce ATP and NADPH powering their metabolism. Harnessing these products for driving biocatalytic reactions would enable to develop clean and sustainable alternatives for chemical reactions. In this study, we present the first demonstration that ATP produced from the photosynthetic process, can fuel a biocatalytic transformation in the whole-cell configuration. This result was achieved by expressing in the cyanobacterium Synechocystis sp. PCC 6803 an ATP-dependent enzyme, the {gamma}-Glutamyl-MethylAmide Synthetase from Methylovorus mays No. 9 (MmGMAS). The expressed enzyme was able to drive in the transgenic strain the light-driven biosynthesis of L-theanine. Consumption of ATP by the recombinant MmGMAS was even beneficial under strong illumination, protecting the photosynthetic electron transport from photodamage. These findings demonstrate the possibility of using photosynthetic microorganisms like Synechocystis as potential platform for sunlight driven biotransformations with wide potential biocatalytic applications. In this perspective, we further present the tridimensional structure of MmGMAS, which explains its promiscuous in vivo activity and provides the basis for its rational evolution.

biochemistry↗

bioRxiv2025

Flavodiiron protein activity outcompetes cyclic electron transport when expressed in angiosperm Nicotiana tabacum

In conditions of excess illumination, alternative electron transport pathways in the thylakoid membranes protect the photosynthetic apparatus against damage from eventual over-reduction. Two main pathways downstream of photosystem I (PSI) enable alternative electron flow, mitigating PSI acceptor-side limitation, while contributing to ATP biosynthesis without reducing NADP+ to NADPH: cyclic electron transport (CET) and pseudo-cyclic electron transport (PCET). Flavodiiron proteins (FLV) are crucial enzymes in PCET, found in all photosynthetic organisms but lost during the evolution of angiosperms. The absence of FLV coding sequences in angiosperm genomes raises intriguing questions about their role and function in photosynthetic organisms. Previous studies utilizing heterologous expression have already demonstrated that FLV can function in angiosperms. In this study, Physcomitrium patens FLVA and FLVB coding sequences were stably expressed in wild-type Nicotiana tabacum, a model crop species. Transgenic lines exhibited significantly increased PCET rates, with FLV-dependent electron transport competing for electrons with CET, particularly under sudden increases in light intensity that limited acceptor side limitation. These findings indicate that FLVs are not only active but also play a critical role in protecting from over-reduction the photosynthetic apparatus of Nicotiana tabacum under fluctuating light conditions.

plant biology↗

bioRxiv2024

Physcomitrium patens flavodiiron proteins form a redox-dependent heterocomplex.

Flavodiiron proteins (FLVs) catalyze the reduction of oxygen to water by exploiting electrons from Photosystem I (PSI). In several photosynthetic organisms such as cyanobacteria, green algae, mosses and gymnosperms, FLV-dependent electron flow protects PSI from over-reduction and consequent damage especially under fluctuating light conditions. In this work we investigated biochemical and structural properties of FLVA and FLVB from the model moss Physcomitrium patens. The two proteins, expressed and purified from Escherichia coli, bind both iron and flavin cofactors and show NAD(P)H oxidase activity as well as oxygen reductase capacities. Moreover, the co-expression of both FLVA and FLVB, coupled to a tandem affinity purification procedure with two different affinity tags, enabled the isolation of the stable and catalytically active FLVA/B hetero multimer protein complex, that has never been isolated and characterized so far. The multimeric organization was shown to be stabilized by inter-subunit disulfide bonds. This investigation provides valuable new information on the biochemical properties of FLVs, with new insights into their in vivo role and regulation.

plant biology↗

bioRxiv2023

A conserved ESCRT-II-like protein participates in the biogenesis and maintenance of thylakoid membranes

Thylakoids are membrane-bound compartments located in cyanobacteria and chloroplasts of plants and algae. They play an indispensable role in the light-driven reactions that enable photosynthetic organisms to convert water and carbon dioxide into oxygen and sugars. The biogenesis and maintenance of thylakoid membranes is a critical yet underappreciated area of research. One of the few known critical regulators of this process, VIPP1 (Vesicle-Inducing Protein in Plastids 1), was recently shown to be structurally similar to ESCRT-III proteins -- the first evidence for ESCRT-like (Endosomal Sorting Complex Required for Transport) machinery in chloroplasts. Here, we used an affinity purification approach in two distantly related photosynthetic eukaryotes, the green alga Chlamydomonas reinhardtii and the plant Arabidopsis thaliana, to discover proteins that interact with VIPP1. Among several newly identified proteins, we focused on a highly conserved but uncharacterized protein (VIPP1-Associated protein 1, VIA1) that robustly interacts with VIPP1 in both systems. VIA1 is predicted to contain a winged-helix domain, a characteristic feature of ESCRT-II proteins that mediates the interaction with ESCRT-III proteins. The absence of VIA1 causes thylakoid swelling upon exposure to high light in Chlamydomonas and defective thylakoid biogenesis in the newly emerging leaf tissue in Arabidopsis, thereby delaying chloroplast development in this tissue. We propose that VIA1 is part of a previously unrecognized chloroplast ESCRT-like system that plays a critical role in forming, remodeling, and repairing photosynthetic membranes. Significance StatementThylakoid membranes are essential for photosynthesis, yet their biogenesis and maintenance are poorly understood. Of the few known proteins involved in these processes, VIPP1 stands out due to its similarity to ESCRT-III, an integral component of the ESCRT machinery that is responsible for membrane remodeling and trafficking in the cytoplasm of eukaryotes. Here we report the discovery of VIA1, a conserved protein that interacts with VIPP1 and participates in thylakoid biogenesis and remodeling in two distantly related photosynthetic organisms. Because VIA1 contains a predicted winged-helix domain, a hallmark feature of ESCRT-II proteins that mediates the interaction with ESCRT-III proteins, our data support the hypothesis that universal, mechanistic principles govern membrane remodeling across all living organisms.

plant biology↗

bioRxiv2020

The state of oligomerization of Rubisco controls the rate of LSU translation in Chlamydomonas reinhardtii

Ribulose 1,5-bisphosphate Carboxylase/Oxygenase (Rubisco) is a key enzyme for photosynthesis-driven life on Earth. While present in all photosynthetic organisms, its most prominent form is a hetero-oligomer in which a Small Subunit (SSU) stabilizes the core of the enzyme built from Large Subunits (LSU), yielding, after a chaperone-assisted multistep assembly, a LSU8SSU8 hexadecameric holoenzyme. Here we use Chlamydomonas reinhardtii, and a combination of site-directed mutants, to dissect the multistep biogenesis pathway of Rubisco in vivo. We identify assembly intermediates, in two of which LSU is associated with the RAF1 chaperone. Using genetic and biochemical approaches we further unravel a major regulation process during Rubisco biogenesis which places translation of its large subunit under the control of its ability to assemble with the small subunit, by a mechanism of Control by Epistasy of Synthesis (CES). Altogether this leads us to propose a model where the last assembly intermediate, an octameric LSU8-RAF1 complex which delivers LSU to SSU to form the Rubisco enzyme, converts to a key regulator form able to exert a negative feed-back on the initiation of translation of LSU, when SSU is not available.

plant biology↗