Biology subjects

Ripamonti, M.

Publications and source records attributed to Ripamonti, M..

4 recordsLinked to original sources

bioRxiv2021

Scaphoideus titanus Ball feeding behaviour on three grapevine cultivars with different susceptibilities to Flavescence doree

Scaphoideus titanus (Ball) is a grapevine-feeder leafhopper, and the most important vector of Flavescence doree of grapevine (FD), a disease associated with phytoplasmas belonging to ribosomal subgroups 16Sr-V-C and -D. FD is a major constraint to viticulture in several European countries and, so far, its control has relied on roguing of infected plants and insecticide applications against the vector. Detailed knowledge on different levels of the multifaceted phytoplasma-plant-vector relationship is required to envisage and explore more sustainable ways to control the disease spread. In the present work, S. titanus feeding behaviour was described on three grapevine cultivars: Barbera (susceptible to FD), Brachetto, and Moscato (tolerant to FD) using the Electrical Penetration Graph (EPG) technique. Interestingly, no differences were highlighted in the non-phloem feeding phases, thus suggesting that the tested cultivars have no major differences in the biochemical composition or structure of the leaf cuticle, epidermis or mesophyll, that can affect the first feeding activities. On the contrary, the results showed significant differences in leafhopper feeding behaviour in terms of the duration of the phloem feeding phase, longer on Barbera and shorter on Brachetto and Moscato, and of the frequency of interruption-salivation events inside the phloem, higher on Brachetto and Moscato. These findings indicate a possible preference for the Barbera cultivar, a better host for the leafhopper. Scaphoideus titanus feeding behaviour on Barbera correlates with an enhanced FDp transmission efficiency, thus explaining, at least in part, the higher susceptibility of this cultivar to FD. The mechanisms for the possible non-preference for Brachetto and Moscato are discussed, and an antixenosis is hypothesized. We propose that breeding for resistance against FD should take into account both plant traits associated with the response to the phytoplasmas and to the vector.

animal behavior and cognition↗

bioRxiv2020

Neural precursor cells contribute to decision-making by tuning striatal connectivity via secretion of IGFBPL-1

The adult brain retains endogenous neural stem/precursors cells (eNPCs) in two major neurogenic niches, the subgranular zone (SGZ) in the hippocampus and the subventricular zone (SVZ). While in humans and rodents the SGZ contributes to memory functions by generating new neurons that integrate into hippocampal circuitry, the role of eNPCs of the SVZ is less clear. SVZ-eNPCs contribute to the generation of new neurons fated to the olfactory bulb (OB) in rodents but not in humans where they are thought to contribute to striatal neurogenesis as a result of tissue damage. Here, we show in mice and humans a novel non-neurogenic physiological role of adult SVZ-eNPCs in supporting cognitive functions by regulating striatal neuronal activity. We first provide evidence that GABAergic transmission between parvalbumin-expressing fast-spiking interneurons (FSIs) and medium spiny neurons (MSNs) is tuned by SVZ-eNPCs via secretion of Insulin-Like Growth Factor Binding Protein Like 1 (IGFBPL-1) that, in turn, regulates the Insulin-Like Growth Factor (IGF-1) signalling cascade. Consistently, selective ablation of SVZ-eNPCs and in vivo disruption of the IGF-signalling determine the impairment of intrastriatal coherence. A finding associated with a higher failure rate of GABAergic transmission mediated by FSIs and with striatum-related behavioural dysfunctions impairing decision making. Human validation studies revealed IGFBPL-1 expression in the SVZ and in foetal and induced-pluripotent stem cell-derived NPCs as well as a strong correlation in neurological patients between SVZ pathological damage, reduction of striatum volume and impairment of information processing speed. All in all, our results highlight a novel non-neurogenic homeostatic role exerted by SVZ-eNPCs on striatal GABAergic neurons that might contribute to cognitive processes involving decisions-making tasks.

neuroscience↗

bioRxiv2020

Silencing of ATP synthase β reduces phytoplasma multiplication in the leafhopper vector Euscelidius variegatus

The leafhopper Euscelidius variegatus is a natural vector of the chrysanthemum yellows phytoplasma (CYp) and a laboratory vector of the Flavescence doree phytoplasma (FDp). Previous studies indicated a crucial role for insect ATP synthase and {beta} subunits during phytoplasma infection of the vector species. Gene silencing of ATP synthase {beta} was obtained by injection of specific dsRNAs in E. variegatus. Here we present the systemic and long-lasting nature of such silencing, its effects on the small RNA profile, the significant reduction of the corresponding protein expression, and the impact on phytoplasma acquisition capability. The specific transcript expression was silenced at least up to 37 days post injection with an average reduction of 100 times in insects injected with dsRNAs targeting ATP synthase {beta} (dsATP) compared with those injected with dsRNAs targeting green fluorescent protein (dsGFP), used as negative controls. Insects injected either with dsATP or dsGFP successfully acquired CYp and FDp during feeding on infected plants. However, the average phytoplasma amount in dsATP insects was significantly lower than that measured in dsGFP specimens, indicating a probable reduction of the pathogen multiplication rate when ATP synthase {beta} was silenced. The role of the insect ATP synthase {beta} during phytoplasma infection process is discussed.

microbiology↗

bioRxiv2019

Somatostatin-Expressing Interneurons Co-Release GABA and Glutamate onto Different Postsynaptic Targets in the Striatum.

The functional contribution of somatostatin-expressing interneurons (SST-INs) to the synaptic organization of the striatum is poorly understood. Using electrophysiological recordings, optogenetic stimulation, and single-cell PCR analysis, we investigated functional patterns of synaptic connectivity in striatal SST-INs expressing channelrhodopsin-2. Photostimulation of these cells induced both glutamatergic excitatory postsynaptic currents (EPSCs) and GABAergic inhibitory postsynaptic currents (IPSCs) in striatal spiny projection neurons (SPNs) and fast-spiking interneurons (FSIs). The two synaptic components showed equally fast onset latencies, suggesting a mechanism of co-transmission. Accordingly, single-cell PCR analysis revealed that individual striatal SST-INs expressed mRNAs for both glutamate and GABA vesicular transporters (VGLUT1 and VGAT, respectively). During relatively prolonged optical stimuli (0.5-1s), IPSC arrays consistently outlasted EPSCs. As a result, photostimulation of SST-INs caused a transient burst of action potentials followed by a prolonged inhibition in postsynaptic cells.\n\nThese data suggest that striatal SST-INs are specialized to locally project synapses exerting a composite excitatory and inhibitory effect through GABA/glutamate co-transmission onto different postsynaptic targets.

neuroscience↗