Biology subjects

Gatti, P.

Publications and source records attributed to Gatti, P..

6 recordsLinked to original sources

bioRxiv2026

Nanoscale remodeling of mitochondrial architecture duringmtRNA surveillance failure

Mitochondria within a cell exhibit heterogeneity in their composition and metabolic functions, and how this specialization shapes the responses of individual organelles to stress is unclear. We applied fluorescence microscopy and in situ cryo-electron tomography to examine the composition of mitochondrial stress bodies and their relationship to inner mitochondrial membrane architecture in the context of a mitochondrial genome expression defect. We discovered that defective mitochondrial RNA processing prompted a loss of inner membrane domain identity, leading to the mislocalization of ATP synthase from cristae edges to the boundary membrane, perturbed cristae morphometrics, and complete cristae loss in a subset of organelles. Mitochondrial stress bodies were enriched with nucleic acid and protein components linked to oxidative pathways, while separate and distinct mitochondrial domains became enriched with oligomerized P5CS, a marker of reductive proline synthesis. We found that consolidation of mitochondrial RNA into stress bodies, as well as ATP synthase remodeling, were regulated independently from P5CS concentration into a subset of the mitochondria. We propose that stress compartmentalization enables independent tuning of the quality control of oxidative pathway components via spatial sequestration from the rest of the mitochondrial network.

cell biology↗

bioRxiv2025

Mitochondrial pull-out controls mitochondrial structure in response to mitochondrial activity

Mitochondrial networks undergo continuous remodeling through fusion and fission, processes that are essential for maintaining energy production and cellular homeostasis. Rapid elongation of the tip of mitochondrial tubules, a process termed dynamic tubulation, also participates in mitochondrial network formation. However, these mechanisms alone cannot fully account for the formation of highly interconnected mitochondrial networks that are required for rapid distribution of mitochondria material. Here, we identify a distinct type of dynamic tubulation, mitochondrial pull-outs characterized by the lateral extrusion from pre-existing mitochondrial tubules, as metabolically regulated determinants of mitochondrial network formation. Pull-outs are distinct from the tip elongation form of dynamic tubulation as they are modulated by the mitochondrial dynamins MFN1 and DRP1 and are stimulated by conditions favoring oxidative phosphorylation. Pull-outs also depend on mitochondrial actin polymerization and are required to increase mitochondrial connectivity and respiratory activity. Together, these findings establish mitochondrial pull-out as a metabolically sensitive mechanism that promotes mitochondrial network connectivity and links organelle architecture to cellular energy demands.

cell biology↗

bioRxiv2025

Long-term impacts of tree monoculture plantations on biodiversity are mediated by soil acidification

Reforestation efforts have sought to counteract deforestation and to provide a nature-based solution against climate change. However, they often involve monoculture plantations of non-native species, which may have unintended ecological consequences. Yet, the long-term impacts of planting trees have been poorly estimated. Leveraging historical reforestation conducted in northern Italy during the 1920s by the fascist regime, we assessed the long-term impacts of red spruce (Picea abies) monoculture plantations on biodiversity of plants and soil fauna. We found that plant diversity in tree plantations was 50.3% lower than in native forests and 74.5% lower than in grasslands. Additionally, functional evenness was reduced by 30% in spruce plantations, suggesting lower ecological stability. In tree plantations, soil pH was significantly more acid and organic carbon content was 25% higher due to litter deposition and slower decomposition rates. Soil fauna diversity was marginally less affected, suggesting a faster recover over the last one-hundred years of arthropods as compared to plants. These findings highlight the need for monitoring reforestation interventions, suggesting strategies that incorporate diverse tree species rather than planting tree monocultures to support functionally and resilient ecosystems.

ecology↗

bioRxiv2024

Impact of Spruce Plantation on Plant Diversity

1As the effects of climate change are becoming more evident, different countries around the world are adopting new policies to intervene on the regulation of greenhouse gasses emission. Recent frameworks acknowledge the potential contribution that forest ecosystems can give to carbon sequestration. These are indicating reforestation programmes as effective climate change mitigation options. Yet, there are possibilities that reforestation may have counteractive effects on biodiversity. However the long term consequences of reforestation for biodiversity are poorly understood. Reforestation policies have already been widely implemented around the world. For instance, in northern Italy and central Europe plantations of spruce trees (Picea abies) have been highly promoted during the last century. The objective of our research is to address the long term consequences of reforestation by answering the following questions. What is the spruce plantations impact on plant diversity? Does the spruce plantation impact environmental factors like luminosity and ground surface temperature and do these environmental factors affect plant diversity? We hypothesize that the spruce plantation causes a reduction of plant diversity. Indeed, we expect that the spruce plantation affects different environmental factors that have an important role in determining plant composition and abundance. To answer our research questions, we have conducted a study in two different sites of the Como Prealps. The potential vegetation of the selected area is represented by mixed forests of deciduous trees dominated by beech trees (Fagus sylvatica). Historically, the land has also been used for grazing and mowing. However, some stands of the potential vegetation are here replaced by spruce plantations, the presence of which is linked to national forestry policies of the twentieth century. For our research we have conducted a total of 100 vegetation surveys to collect data on plant diversity and environmental factors, namely luminosity and ground surface temperature. We then compared plant diversity among land-use treatments (i.e., habitat types): the spruce plantation, the natural mixed forest and the semi-natural grassland-pasture. For our analysis we have used linear regression models to test the impact of the different habitat types on plant diversity. We have also measured covariance and correlation to analyse the relationship between the environmental factors and plant diversity. The analysis on plant diversity reveals the long-lasting impact of spruce monoculture plantation on plant diversity. The number of plant species decreases by 57percent from the grassland-pasture to the spruce plantation and by 41percent compared to the natural mixed forest. Likewise, the diversity of plant functional forms decreases in the spruce plantation as compared to mixed forests and grassland-pasture. At last, although luminosity and ground surface temperature do not vary from the mixed forest to the spruce plantation, we have measured a positive relationship between the number of plant species and the two environmental parameters. Our research provides novel evidence that the spruce plantation negatively impacts plant diversity still one hundred years after. As biodiversity loss and climate change are two interwoven processes, they must not be treated separately. For what concerns future reforestation programmes, we recommend that they include biodiversity-friendly measures and address win-win solutions, for their effectiveness in climate change mitigation would otherwise be compromised.

ecology↗

bioRxiv2024

Extracellular matrix signals promotes actin-dependent mitochondrial elongation and activity

Mitochondria are crucial metabolic organelles that are regulated by both intracellular and extracellular cues. The extracellular matrix (ECM) is a key component of the cellular environment that controls cellular behavior and metabolic activity. Here, we determined how ECM signalling regulates mitochondrial structure and activity. To distinguish mitochondrial regulation from the general survival cues generated by the ECM, we used breast cancer-derived spheres (mammospheres) because of their ability to grow in suspension culture in the absence of ECM. Using this system, we demonstrate that the association of mammospheres with the ECM results in dramatic mitochondrial elongation, along with enhanced mitochondrial respiration and ATP production. This remodeling occurs independently of DRP1 activity, but relies on integrin signaling and actin polymerization. Therefore, our findings demonstrate that ECM-driven actin polymerization plays a crucial role in remodeling mitochondrial networks to promote OXPHOS, which represents a vital step for migrating cells to enhance cellular adhesion and facilitate cell growth.

cell biology↗

bioRxiv2023

Mitochondria- and ER-associated actin are required for mitochondrial fusion

Mitochondria play a crucial role in the regulation of cellular metabolism and signalling. Mitochondrial activity is modulated by the processes of mitochondrial fission and fusion, which are required to properly balance respiratory and metabolic functions, transfer material between mitochondria, and remove defective mitochondria. Mitochondrial fission occurs at sites of contact between the endoplasmic reticulum (ER) and mitochondria, and is dependent on the formation of actin filaments that drive mitochondrial constriction and the recruitment and activation of the dynamin-related GTPase fission protein DRP1. The requirement for mitochondria- and ER-associated actin filaments in mitochondrial fission remains unclear, and the role of actin in mitochondrial fusion remains entirely unexplored. Here we show that preventing the formation of actin filaments on either mitochondria or the ER disrupts both mitochondrial fission and fusion. We show that fusion but not fission is dependent on Arp2/3, whereas both fission and fusion are dependent on INF2 formin-dependent actin polymerization. We also show that mitochondria-associated actin marks fusion sites prior to the dynamin family GTPase fusion protein MFN2. Together, our work introduces a novel method for perturbing organelle-associated actin filaments, and demonstrates a previously unknown role for actin in mitochondrial fusion.

cell biology↗