The role of Xylella fastidiosa extracellular vesicles and sRNAs in cell-to-cell communication

Ruf, Alessa (2026): The role of Xylella fastidiosa extracellular vesicles and sRNAs in cell-to-cell communication. Dissertation, LMU München: Fakultät für Biologie

Abstract

A hallmark of plant infections with microbes is the extensive shuttle of molecules between the interaction partners. Extracellular vesicles (EVs) have emerged as important players in the transfer of protein and nucleic acid signals between microbes and their plant hosts. The bacterial plant pathogen Xylella fastidiosa (Xf) colonizes the xylem of a wide array of host plants leading to devastating diseases in agriculturally important crops such as olive, grapevine and almond. To infect systemically, Xf relies on the shift between planktonic and biofilm lifestyle, a quorum-sensing dependent process mediated by the release of Xf-EVs. We aimed to understand if Xf-EVs also play a role in delivering molecules to recipient cells. For this, we catalogued the protein, DNA and RNA cargo of Xf-EVs, which positions EVs as mediators of horizontal gene transfer in Xf. A major EV-associated genomic island encodes a class of small non-coding RNA, coined sXFs. First functional analysis of EV-delivered sXFs proposes cross-kingdom RNA interference-mediated regulation of plant immune receptors. Given the presence of conserved Hfq-binding motifs at one of the sXFs loops, we further characterized the role of the EV-associated RNA chaperone Hfq and its bound sRNAs, revealing RNA-based regulation as a major contributor for cell-to-cell communication and lifestyle switches in Xf, which in turn mediates the bacterium’s virulence. On the plant side, we identify Argonaute 1 as a negative regulator of Xf infection in Arabidopsis revealing the involvement of RNA interference in plant resistance to infections with Xf. Taken together, this work extends knowledge on how Xf-EVs act as extracellular communication tools for Xylella fastidiosa by (i) spreading genomic islands, (ii) silencing plant immunity receptors, potentially mediated by the delivery of sXFs, and (iii) facilitating the delivery of Hfq-bound sRNAs to mediate colony-wide lifestyle switches. It further highlights the importance of RNA-mediated regulation in plant infections with Xf, both on the plant and on the bacterial site. This adds a new molecular layer to our understanding of the virulence of this economically important plant pathogen.

• Dokumententyp: Dissertationen (Dissertation, LMU München)
• Themengebiete: 500 Naturwissenschaften und Mathematik ; 500 Naturwissenschaften und Mathematik > 570 Biowissenschaften, Biologie
• Fakultäten: Fakultät für Biologie
• Sprache der Hochschulschrift: Englisch
• Datum der mündlichen Prüfung: 13. Februar 2026
• 1. Bericht­erstatter:in: Robatzek, Silke