Biology subjects

Alboresi, A.

Publications and source records attributed to Alboresi, A..

11 recordsLinked to original sources

bioRxiv2026

Evolutionary co-option of the ancient protein AMBRA1 in plant photomorphogenesis

Photomorphogenesis, the light-driven developmental program of plants, is repressed in darkness by the CUL4-DDB1-COP1 ubiquitin ligase complex. In animals, AMBRA1 is a substrate receptor for the same CUL4-DDB1 machinery, regulating proteostasis, cell proliferation and autophagy, but its role in plants has remained unknown. Here we show that the moss Physcomitrium patens carries two light-regulated AMBRA1 genes, AMBRA1a and AMBRA1b, whose loss impairs vegetative growth and cell-fate transitions under light and prevents the elongation of gravitropic filaments in darkness, indicating that AMBRA1 is required to repress photomorphogenesis. AMBRA1 localizes to the nucleus under both long-day and dark conditions, and its loss causes widespread transcriptional reprogramming of developmental and metabolic pathways, including repression of photosynthesis-related genes in darkness. These findings identify AMBRA1 as a previously unrecognized nuclear regulator that links light availability to plant growth and as a key repressor of photomorphogenesis.

plant biology↗

bioRxiv2026

Evolutionary insights into β-cyclocitral signaling in Physcomitrium patens

How did a product of photooxidative damage become a signal for stress tolerance? {beta}-cyclocitral ({beta}-cc) promotes acclimation in several angiosperms, yet has detrimental effects in other photosynthetic organisms. We investigated this contrast in the moss Physcomitrium patens to explore the evolution of {beta}-cc signaling. We combined apocarotenoid treatments and excess light exposure with photosynthetic measurements, biochemical analyses and RNA sequencing. Comparative phylogenomics traced the conservation of regulatory and detoxification components associated with {beta}-cc responses. Physcomitrium accumulated {beta}-cc under excess light and mounted a strong transcriptional response to exogenous {beta}-cc, substantially overlapping with its light-stress response. Nevertheless, {beta}-cc impaired photosynthetic performance and provided no protection. At a phylogenetic level, while MBS1 was deeply conserved, the downstream detoxification module showed marked divergence. Notably, ANAC081/ANAC102-like proteins were recovered in terrestrial monocots but not in Physcomitrium or Lemna turionifera, both showing detrimental responses to {beta}-cc. Our findings suggest that the evolution of protective {beta}-cc signaling involved the recruitment of downstream detoxification regulators, with the SCL14/TGAII- and ANAC081/ANAC102-related lineage emerging as a candidate link between an ancient oxidative cue and beneficial acclimation.

plant biology↗

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

Inactivation of mitochondrial complex IV in Physcomitrium patens reveals the essential role of respiration in coordinating plants metabolism

Photosynthetic organisms use sunlight as energy source but rely on respiration during the night and in non-photosynthetic tissues. Respiration is also active in photosynthetically active cells, where its role is still unclear due to a lack of viable mutants. Plants lacking cytochrome c oxidase (complex IV) activity are generally lethal but were here isolated exploiting the possibility of generating knockout lines through vegetative propagation in the moss Physcomitrium patens. The mutants showed severely impaired growth, with an altered composition of the respiratory apparatus and increased electron transfer through the alternative oxidase. The light phase of photosynthesis remained largely unaffected while the efficiency of carbon fixation was moderately reduced. Transcriptomic and metabolomic analyses showed that the disruption of the cytochrome pathway had broad consequences for carbon and nitrogen metabolism. A major alteration in nitrogen assimilation was observed with a general reduction in amino acid abundance. A partial rescue of the growth could be obtained by growing the plants with an external supply of amino acids but not with sugars, demonstrating that respiration in plant photosynthetic cells plays an essential role at the interface between carbon and nitrogen metabolism and a key role in providing carbon skeletons for amino acid biosynthesis.

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↗

bioRxiv2024

Mitochondrial respiration is essential for photosynthesis-dependent ATP supply of the plant cytosol

Plants rely on solar energy to synthesize ATP and NADPH for photosynthetic carbon fixation. Since a substantial proportion of cellular ATP is consumed in the cytosol, photosynthesis-derived ATP needs to be supplied there. While the triose phosphate shuttle and mitochondrial respiration can both deliver ATP to the cytosol, the significance of the different mechanisms in vivo has been difficult to assess. Although mitochondrial respiration is essential in plants, whether this is due to heterotrophic bottlenecks during plant development or rather a need for respiration in photosynthetically active cells, has not been resolved. In this study, we examined in vivo changes of cytosolic ATP concentration in response to light, employing a biosensing strategy in the moss Physcomitrium patens. Our measurements revealed increased cytosolic ATP concentration caused by photosynthetic activity. Moss tissue depleted of respiratory complex I showed decreased cytosolic ATP accumulation, highlighting a critical role of mitochondrial respiration in light-dependent ATP supply of the cytosol. Consistently, targeting mitochondrial ATP production directly, through the construction of mutants deficient in mitochondrial ATPase (complex V), led to drastic growth reduction, despite only minor alterations in photosynthetic electron transport activity. Since P. patens is photoautotrophic throughout its development, we conclude that heterotrophic bottlenecks cannot account for the indispensable role of mitochondrial respiration in plants. Instead, our results offer compelling evidence that mitochondrial respiration is essential for ATP provision to the cytosol in actively photosynthesizing cells. Mitochondrial respiration provides metabolic integration, ensuring a reliable supply of cytosolic ATP essential for supporting plant growth and development.

plant biology↗

bioRxiv2022

Functional analysis of PsbS transmembrane domains through base editing in Physcomitrium patens

Plants exposed to light fluctuations are protected from photodamage by non-photochemical quenching (NPQ), a reversible mechanism that enables dissipation of excess absorbed energy as heat, which is essential for plant fitness and crop productivity. NPQ requires the activity of the membrane protein PsbS that, upon activation, interacts with antenna proteins, inducing their dissipative conformation. Here, we exploited base editing in the moss Physcomitrium patens to introduce in vivo specific amino acid changes and assess their impact on PsbS activity, targeting transmembrane regions to investigate their role in protein-protein interactions. This approach enabled the recognition of residues essential for protein stability and the identification of a hydrophobic cluster of amino acids with a seminal role in PsbS activity. This work provides new information on the PsbS molecular mechanism while also demonstrating the potential of base editing approaches for in planta gene function analysis.

plant biology↗

bioRxiv2020

Inactivation of mitochondrial Complex I stimulates chloroplast ATPase in Physcomitrella (Physcomitrium patens).

While light is the ultimate source of energy for photosynthetic organisms, mitochondrial respiration is still fundamental for supporting metabolism demand during the night or in heterotrophic tissues. Respiration is also important for the metabolism of photosynthetically active cells, acting as a sink for excess reduced molecules and source of substrates for anabolic pathways. In this work, we isolated Physcomitrella (Physcomitrium patens) plants with altered respiration by inactivating Complex I of the mitochondrial electron transport chain by independent targeting of two essential subunits. Results show that the inactivation of Complex I causes a strong growth impairment even in fully autotrophic conditions in tissues where all cells are photosynthetically active. Complex I mutants show major alterations in the stoichiometry of respiratory complexes while the composition of photosynthetic apparatus was substantially unaffected. Complex I mutants showed altered photosynthesis with higher yields of both Photosystems I and II. These are the consequence of a higher chloroplast ATPase activity that also caused a smaller {Delta}pH formation across thylakoid membranes as well as decreased photosynthetic control on cytochrome b6f, possibly to compensate for a deficit in ATP supply relative to demand in Complex I mutants. These results demonstrate that alteration of respiratory activity directly impacts photosynthesis in P. patens and that metabolic interaction between organelles is essential in their ability to use light energy for growth.

plant biology↗

bioRxiv2020

The activity of chloroplast NADH dehydrogenase-like complex influences the photosynthetic activity of the moss Physcomitrella patens

Alternative electron pathways contribute to the regulation of photosynthetic light reactions to meet metabolic demands in a dynamic environment. Understanding the molecular mechanisms of their activity is seminal to decipher their role in response to environmental cues and in plant adaptation. The chloroplast NADH dehydrogenase-like (NDH) complex mediates cyclic electron transport pathway around photosystem I (PSI) in different organisms like cyanobacteria, algae and various plant species but has a discontinuous distribution in the green lineage. In order to assess how its activity and physiological role changed during plant evolution, we isolated Physcomitrella patens lines knocked out of the gene NDHM which encodes for a subunit fundamental for the stability and activity of the whole complex. P. patens ndhm KO mosses showed high PSI acceptor side limitation upon illumination leading to PSI photoinhibition. Flavodiiron proteins (FLV) have similar and particularly important role in preventing PSI overreduction when plants are exposed to light fluctuations. The flva ndhm double KO mosses alteration in photosynthetic parameters leaded to a defect in plant growth under fluctuating light as compared to WT and single KO mutants. Results evidenced that, while FLV sustain strong electron transport after an abrupt change in light intensity, NDH contribution to electron transport is small. NDH still participate in modulating PSI activity and it is seminal to prevent PSI photoinhibition especially when FLV are inactive. In plants the functional overlap between NDH- and FLV-dependent electron transport systems sustains PSI activity and to prevent its photoinhibition.

plant biology↗

bioRxiv2019

Regulation of electron transport is essential for photosystem I stability and plant growth

Life depends on the ability of photosynthetic organisms to exploit sunlight to fix carbon dioxide into biomass. Photosynthesis is modulated by pathways such as cyclic and pseudocyclic electron flow (CEF and PCEF). CEF transfers electrons from photosystem I to the plastoquinone pool according to two mechanisms, one dependent on proton gradient regulators (PGR5/PGRL1) and the other on the type I NADH dehydrogenase (NDH) complex. PCEF uses electrons from photosystem I to reduce oxygen; in several groups of photosynthetic organisms but not in angiosperms, it is sustained by flavodiiron proteins (FLVs). PGR5/PGRL1, NDH and FLVs are all active in the moss Physcomitrella patens, and mutants depleted in these proteins show phenotypes under specific light regimes. Here, we demonstrated that CEF and PCEF exhibit strong functional overlap and that when one protein component is depleted, the others can compensate for most of the missing activity. When multiple mechanisms are simultaneously inactivated, however, plants show damage to photosystem I and strong growth reduction, demonstrating that mechanisms for the modulation of photosynthetic electron transport are indispensable.

plant biology↗

bioRxiv2018

Exploration of plant biodiversity to investigate regulation of photosynthesis in natural environment

Photosynthesis is regulated in response to dynamic environmental conditions to satisfy plant metabolic demand but also to avoid over-excitation of the electron transport chain generating harmful reactive oxygen species. Photosynthetic organisms evolved several mechanisms to modulate light harvesting and electron transport efficiency to respond to conditions changing at different timescales, going from fast sun flecks to slow seasonal variations.\n\nThese regulatory mechanisms changed during evolution of photosynthetic organisms, also adapting to various ecological niches. The investigation of plant biodiversity is valuable to uncover conserved traits and plasticity of photosynthetic regulation. In this work a set of plants belonging to different genera of angiosperms, gymnosperms, ferns and lycophytes was investigated by monitoring their photosynthetic parameters in different seasons, looking for common trends and differences. In all plants analysed photosynthetic electron transport rate was found to be modulated by growth light intensity, ensuring a balance between available energy and photochemical capacity. Growth light also influenced the threshold where heat dissipation of excitation energy, also called Non-Photochemical Quenching (NPQ), was activated. On the contrary NPQ amplitude did not correlate with light intensity experienced by the plants but was a species-specific feature.\n\nNPQ zeaxanthin-dependent component, qZ, was found to be the most variable between different plants, modulating the intensity of the response but also the kinetic properties of its activation and relaxation. The slower NPQ component, qI, was instead found to be uncorrelated with photoinhibition eventually suffered by plants.

plant biology↗