Investigation of plant genetic-microbiome interactions in different plant species

The rhizosphere, i.e. the soil surrounding the plant roots, and endosphere, i.e. the microbial communities within the plant organs harbors microbes known to influence root and plant physiological processes. An important question is to what extent plant species, genotypes and environmental conditions affect bacterial and fungal communities. The objectives of the first research study were to unravel and compare the rhizospheric microbiota of grape in two independent vineyards using 16S and ITS amplicon sequencing, evaluate location and varietal effects, and test the correlation between bioavailable copper levels and other soil parameters with microbiota composition and diversity. Our results showed that the microbial alpha diversity based on Shannon index differed significantly between vineyards while it did not differ between two grape cultivars. In the second study, we were focusing on different wheat species and genotypes such as Bread Wheat, Wild Emmer Wheat, Domesticated Emmer Wheat, Durum Wheat Landraces, Durum Wheat cultivars, T. monococcum and triticale in two fields located in Bologna and Foggia. The objectives of this research experiment were to elucidate and compare the rhizospheric and endophytic microbiota of 30 diverse wheat genotypes in two different fields using 16S amplicon sequencing. Our results showed that the microbial alpha diversity based on Shannon index differed significantly between fields of Bologna and Foggia, in which Bologna had a higher diversity in respect to Foggia for both rhizospheric and endophytic communities. Using Shannon index there was significant differences, for instance, between Durum Emmer Wheat and Wild Emmer Wheat in Bologna, and between Bread Wheat and Durum Wheat Landraces in Foggia. Our results contribute to understand the role of wheat species and genotype and the filed management on the root-microbe-soil interactions in the perspective of understanding their impact on crop systems sustainability.

Drosophila melanogaster as a model to study host-parasitoid interactions: the case of the polydnaviral protein TnBVANK1

Parasitic wasps attack a number of insect species on which they feed, either externally or internally. This requires very effective strategies for suppressing the immune response and a finely tuned interference with the host physiology that is co-opted for the developing parasitoid progeny. The wealth of physiological host alterations is mediated by virulence factors encoded by the wasp or, in some cases, by polydnaviruses (PDVs), unique viral symbionts injected into the host at oviposition along with the egg, venom and ovarian secretions. PDVs are among the most powerful immunosuppressors in nature, targeting insect defense barriers at different levels. During my PhD research program I have used Drosophila melanogaster as a model to expand the functional analysis of virulence factors encoded by PDV focusing on the molecular processes underlying the disruption of the host endocrine system. I focused my research on a member of the ankyrin (ank) gene family, an immunosuppressant found in bracovirus, which associates with the parasitic wasp Toxoneuron nigriceps. I found that ankyrin disrupts ecdysone biosynthesis by impairing the vesicular traffic of ecdysteroid precursors in the cells of the prothoracic gland and results in developmental arrest.

Genomic and functional insights into the interactions between vaginal Lactobacillus strains and pathogens

The vaginal microbiota of healthy pre-menopausal women is typically dominated by one Lactobacillus species among L. crispatus, L. gasseri, L. jensenii and L. iners. Thanks to a series of antimicrobial activities, strains belonging to these species represent the first barrier against infections and maintain niche homeostasis. On the other hands, the increase abundance in pathogen species is associated with the onset of numerous diseases, leading also to an increase risk of other infections acquisition. The deciphering of factors which influence Lactobacillus survival, as well as the interactions between lactobacilli-pathogens and pathogens-pathogens represent an important topic of study for improving woman health and investigating effective probiotic strategies. Here, we investigated environmental factors and genetic traits that lead to the dominance of either L. crispatus or L. gasseri in the vaginal niche and the possible applications of liposomes loaded with L. gasseri biosurfactants for the treatment and prevention of Staphylococcus aureus biofilm infections. Furthermore, considering the increasing relevance acquired by bacterial extracellular vesicles (EVs) we analysed the role of EVs derived from vaginal lactobacilli and pathogens on both bacterial growth and HIV-1 infections. As a result, we reported for the first time i) common and species-specific genotypic and phenotypic features of L. crispatus and L. gasseri ii) significant antibiofilm activity of liposomes loading vaginal Lactobacillus biosurfactants against multi-drug resistant S. aureus strains iii) absence of growth regulation mediated by EVs derived from lactobacilli on pathogen cultures and vice versa iv) anti-HIV-1 activity of protein derived from L. gasseri EVs and unexpected antiviral effect of pathogen-derived EVs on HIV-1 infections in vitro. In conclusion, this PhD thesis explored characteristics and possible applications of vaginal lactobacilli for the human health, as well as promising antiviral effects of both lactobacilli and pathogen derived EVs.