Exploring the host responses of wheat and barley to the Bacterial Leaf Streak (BLS) pathogen, Xanthomonas translucens

Abstract

Bacterial Leaf Streak (BLS) is found in nearly all wheat and barley-growing regions of the world and is caused by the re-emerging pathogen Xanthomonas translucens (Xt). There are limited resources regarding the molecular mechanisms of Xt virulence and the host immune response. This present research describes the molecular interface between Xt and its cereal hosts by exploring the pathogen virulence factors and plant immunity. Using long-read whole genome sequencing and comparative genomes of recently collected Xt isolates from Colorado showed a conserved core Type III effector repertoire across strains. However, highly virulent strains showed a diverse Transcription Activator-Like (TAL) effector repertoire with potential chromosomal re-arrangements. Functional validation using marker-free deletions of TAL effectors in a highly virulent strain identified specific effectors that could play a role in increased virulence and host physiology. Moreover, we investigate how the host immune suppression by xanthan also contributes to virulence and explore how the cereal immune system recognizes a proteinaceous microbe-associated molecular pattern (MAMP) shared between pathovars. Our findings bridge in-silico predictions with in-planta functional characterization of host immunity and pathogen virulence factors to explore the dynamics of plant-microbe interactions in order to provide strategies for developing durable plant disease resistance.