Biology subjects

Fontana, A.

Publications and source records attributed to Fontana, A..

3 recordsLinked to original sources

bioRxiv2023

Proteomic Analysis Reveals the Molecular Pathways Responsible for Solar UV-B Acclimation in High-altitude Malbec Berries

Grapevine cultivation at high altitudes provides a viable option for producing premium quality wines in the context of climate change. This is primarily attributed to cooler temperatures, wider thermal amplitudes, and increased UV-B radiation. Although high UV-B levels can cause oxidative-stress, grape berries acclimate by generating UV-blocking anthocyanins and antioxidant compounds accumulated in the berry skins, thereby enhancing the organoleptic qualities and aging capacity of wine. This UV-B exclusion study examines how Malbec berries respond to solar UV-B at a high-altitude vineyard in Mendoza, Argentina (1350 m a.s.l.). The results showed that high solar UV-B acts both as a photomorphogenic signal and a stressor. The proteomic changes of berries exposed to +UV-B conditions indicate a decrease of photosynthesis and oxidative phosphorylation, coupled with an increase of glycolysis and tricarboxylic acid cycle as compensatory respiration pathways. Furthermore, numerous chaperones and proteins associated with the antioxidant system exhibited increased abundance to maintain cellular homeostasis. Lastly, veraison-stage berries exposed to +UV-B displayed an activation of the UVR8 signaling cascade and the phenylpropanoid pathway, resulting in higher concentration of phenolic compounds and more oxidation-resistant types of anthocyanins. This is the first report of field-grown grape berry proteomic modulation in response to solar UV-B, and it may have significant implications for the cultivation of high-quality wine grapes in both current and future climate scenarios. Significance

plant biology↗

bioRxiv2023

Multiscale modelling of chromatin 4D organization in SARS-CoV-2 infected cells

SARS-CoV-2 is able to re-structure chromatin organization and alters the epigenomic landscape of the host genome, though the mechanisms that produce such changes are still poorly understood. Here, we investigate with polymer physics chromatin re-organization of the host genome, in space and time upon SARS-CoV-2 viral infection. We show that re-structuring of A/B compartments is well explained by a re-modulation of intra-compartment homotypic affinities, which leads to the weakening of A-A interactions and enhances A-B mixing. At TAD level, re-arrangements are physically described by a general reduction of the loop extrusion activity coupled with an alteration of chromatin phase-separation properties, resulting in more intermingling between different TADs and spread in space of TADs themselves. In addition, the architecture of loci relevant to the antiviral interferon (IFN) response, such as DDX58 or IFIT, results more variable within the 3D single-molecule population of the infected model, suggesting that viral infection leads to a loss of chromatin structural specificity. Analysis of time trajectories of pairwise gene-enhancer and higher-order contacts reveals that such variability derives from a more fluctuating dynamics in infected case, suggesting that SARS-CoV-2 alters gene regulation by impacting the stability of the contact network in time. Overall, our study provides the first polymer-physics based 4D reconstruction of SARS-CoV-2 infected genome with mechanistic insights on the consequent gene mis-regulation.

biophysics↗

bioRxiv2023

Cystine/glutamate antiporter system Xc- deficiency impairs insulin secretion.

System Xc-, encoded by Slc7a11, is an antiporter that exports glutamate and imports cystine. Cystine is used for protein synthesis and incorporation in thiol peptides such as glutathione, which function as cofactors for reactive oxygen species scavenging enzymes. Glutamate export by astrocytes through system Xc- has been implicated in excitotoxicity, a form of neurotoxicity that has been postulated to also occur in insulin-producing beta-cells in the pancreatic islets. This study describes the implications of Slc7a11 deficiency on glucose metabolism in both constitutive and myeloid cells-specific knockout mice. Constitutive Slc7a11 deficiency leads to drastically lowered glutathione levels in the pancreatic islets and immune cells in addition to diminished insulin secretion both in vitro and in vivo. Macrophage-specific deletion did not have a significant impact on metabolism or islet function. These findings suggest that system Xc- is required for glutathione maintenance and insulin production in beta-cells, but is dispensable for islet macrophage function.

molecular biology↗