Biology subjects

Beraldo, C.

Publications and source records attributed to Beraldo, C..

5 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↗

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

Species-associated bacterial diversity increases along a gradient of habitat degradation

Alterations of microbial communities have evident impacts on development, digestion, fecundity, metabolism, immunity, and diverse other biological functions of their hosts. Yet, the factors affecting microbial communities associated with wild species often remain uncharacterized. For example, the impact of the hosts habitat degradation due to anthropogenic activities has received little attention, which contrasts with the large literature showing how such habitat degradation is at least partly responsible for the on-going global patterns of macro-biodiversity erosion. Here, we use metacommunities of herbivorous insect species specialized in feeding on Plantago lanceolata in the fragmented landscape of the [A]land Islands, Finland, as a model system to test whether and how bacterial communities associated with wild species change along a gradient of habitat degradation. We evaluated microbial species diversity and community composition in two sympatric insect species sampled from local meadow habitats with various levels of human disturbance within or around these habitats (e.g. forests, roads, agriculture fields, buildings). Counter to our expectations, we found that bacterial diversity can increase with habitat degradation, with individuals from more degraded habitats hosting more rare bacterial species. In contrast, as the dominant microbial species remain similar across habitats, the community composition and function of the microbiota persist under habitat degradation. In this system, the strength of human activities might induce changes in habitat heterogeneity rather than changes in overall habitat quality, thus allowing local insects to encounter and host more rare microbes rather than trigger local microbial extinction.

microbiology↗

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↗