Unraveling virulence regulation in pectinolytic bacteria: Insights from ArcZ and RsmC. How do these molecular maestros shape virulence in the Dickeya genus?

Doctorante : Typhaine BRUAL 

Laboratoire INSA : MAP

Ecole doctorale : ED341 : Évolution, Écosystèmes, Microbiologie, Modélisation

Pectinolytic bacteria of the genus Dickeya thrive in diverse ecological niches including water, soil and plants, adapting to complex and ever-changing environments shaped by various biotic and abiotic interactions.
In this thesis, we investigated the mechanisms that regulate the virulence of the genus Dickeya, in particular D. dadantii and D. solani.
Our main findings concern post-transcriptional regulation exerted by the sRNA ArcZ and post-translational regulation modulated by the protein RsmC.
ArcZ is a key player in D. solani adaptation, regulating motility according to environmental conditions and enhancing virulence during plant infection. In addition, ArcZ plays a critical role in acid resistance.
RsmC, in turn, is involved in the regulation of motility and has a complex role in virulence. Our results suggest novel interactions for RsmC and open perspectives for studying other undocumented functions.
In a word, our study reveals how regulators such as ArcZ and RsmC orchestrate bacterial responses to a dynamic environment. These findings highlight the adaptability of Dickeya species and underscore the importance of ecological context in the study of bacterial behavior.

Research and study of A1b type entomotoxins: Application for the protection against the pest of tomato, Tuta absoluta

Doctorante :  Fatima Diya

Laboratoire INSA : BF2I

Ecole doctorale : ED 341 : Evolution, Ecosystèmes, Microbiologie, Modélisation

Pea albumin 1 subunit b, PA1b, is a plant cystine knot peptide, extracted from the seeds of peas Pisum sativum and is composed of 37 amino acids. It is a potential candidate for use to control economic pests such as cereal weevils, major pests of stored grains. The natural diversity of this peptide in the seeds of legumes native to the Middle East and belonging to the Faboideae subfamily was investigated. Additionally, the insecticidal activity of each of the seed flour from the selected seeds were evaluated against the susceptible and resistant strains of weevils. This has led to the identification of Vicia sativa ssp. sativa, a promising species containing potent A1b isoforms. The latter from different geographical regions of this species were biochemically characterized, and their biological activities were evaluated. A putative A1b sequence has been identified from Vicia sativa ssp sativa originating from Turkey. Previously, AG41, a 10-fold more toxic isoform was also identified from the roots of Medicago truncatula. In this study, we have identified the key residues responsible for the enhanced toxicity of this peptide using NMR. As a promising bio insecticide targeting the VATP-ase, a proton pump necessary for the absorption of nutrients, PA1b has been also tested on the major pest of tomato, Tuta absoluta. The peptide delivered through injection was lethal to the larval stage of the pest. This has raised interesting prospects about the potential targets of PA1b in insects.