Date of Award
1-24-2024
Degree Name
Doctor of Philosophy (PhD)
Degree Type
Dissertation
Abstract
Bacterial pathogens threaten crop production worldwide, which highlights the need to understand plant and pathogen interactions. Studies on plant-pathogen interactions typically focus on a single host and pathogen. However, bacteria exist in complex microbial communities, not alone. There are few studies that examine the mechanisms behind multi-pathogen infections which renders a gap in our understanding of the subsequent implications on agriculture. In this dissertation, I use in vitro plate assays with RNA-sequencing and in planta assays to investigate the interactions between two cotton bacterial pathogens, Xanthomonas citri pv. malvaearum (Xcm) and Pseudomonas syringae (Ps). In vitro plate assays demonstrate that the bacteria can interact outside their host and that Xcm can prompt directional movement in Ps. RNA-sequencing along with studying genetic mutants revealed that iron-sensing in Ps plays a role in this interaction, and that the movement is independent of typical movement appendages, flagella and Type-4 pili. For in planta interactions, sequential infiltrations and microscopy suggest that both bacteria can colocalize in cotton and that a cotton defense response, once initiated by Xcm first, is effective against Ps. I also explore the presence of genetic resistance to either pathogen in cotton by screening a diversity panel of 253 accessions. This screen revealed that cotton lacks resistance to Ps. Sixty-one accessions showed strong resistance responses to Xcm. This work expands our broad understanding of how bacteria can interact and, more specifically, the interaction dynamics between Ps and Xcm and the potential implications in cotton.
Language
English (en)
Chair and Committee
Rebecca Bart
Committee Members
Barbara Kunkel; Blake Meyers; Christina Stallings; Rachel Penczykowski
Recommended Citation
Harris, Taylor, "A Dynamic Duo: Investigating the Interactions between Xanthomonas citri pv. malvacearum and Pseudomonas syringae" (2024). Arts & Sciences Electronic Theses and Dissertations. 3296.
https://openscholarship.wustl.edu/art_sci_etds/3296