Semester of Graduation

August 2026

Degree

Master of Science (MS)

Department

Plant Pathology & Crop Physiology

Document Type

Thesis

Abstract

Pantoea ananatis is an emerging, versatile bacterial pathogen of increasing concern in Louisiana rice production, where it co-occurs with Burkholderia glumae, the established causal agent of bacterial panicle blight. A population-scale comparative genomic analysis of 136 non-redundant, high-quality genomes reconstructed the species pangenome and revealed an open genome shaped extensively by horizontal gene transfer. Recombination-corrected phylogenetics and Bayesian clustering resolved two deeply divergent, host-associated lineages with distinct functional repertoires, identifying lineage-specific gene families that support differences in host association, geographic distribution, and metabolic capacity. Transcriptional profiling compared both pathogens under monoculture and co-culture conditions at early infection timepoints. B. glumae mounted a modest, temporally stable response of a few hundred differentially expressed genes, whereas P. ananatis underwent massive transcriptional remodeling. Hundreds of genes showed time-dependent reversals, indicating extensive condition-dependent reprogramming and inversion of normal growth-phase transcriptional programs in the presence of a competitor. Co-infection assays then tested the disease consequences of these interactions across vegetative and reproductive developmental stages, using single-pathogen treatments as positive controls. Simultaneous inoculation consistently produced disease severity exceeding either pathogen alone, with all co-inoculated replicates reaching maximum severity by fifteen days post-inoculation, providing direct evidence of a synergistic interaction. Together, these findings link genomic diversity, transcriptional behavior, and disease outcome, demonstrating that both pathogens interact synergistically in rice and establishing a multi-level foundation for understanding bacterial co-pathogenesis and for developing improved diagnostic and management strategies.

Date

7-16-2026

Committee Chair

Ham, Jong Hyun

LSU Acknowledgement

1

LSU Accessibility Acknowledgment

1

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