The two-component regulator CvsR has a small core regulon in planta and modulates Pseudomonas syringae global gene expression with some overlap to the patte

Pattern-triggered immunity (PTI) provides broad-spectrum protection in plants by activating defense responses upon perception of conserved microbial signatures such as bacterial flagellin. In vitro transcriptome profiling revealed that the Pseudomonas syringae pv. tomato DC3000 two-component regulator CvsR mirrors some of the broader regulatory patterns observed under the exposure to PTI in planta . Our analyses indicated that during infection in planta , CvsR primarily governs a small core regulon centered on carbonic anhydrase and its associated transporter. Comparative RNA-seq analyses between the Δ cvsR and wild-type strain further confirm this narrow regulatory scope. Moreover, the majority of bacterial transcriptional shifts appear to reflect indirect consequences of response to the host immune environment rather than direct CvsR-dependent regulation, including responses associated with sulfate starvation. Together, these findings suggest that PTI-driven bacterial transcriptional reprogramming is shaped predominantly by host immune status, with CvsR exerting modest, targeted control restricted to a limited set of genes.

IMPORTANCE

Pattern-triggered immunity (PTI) provides broad-spectrum disease resistance in plants by recognizing conserved microbial patterns such as bacterial flagellin. Activation of PTI alters the environment that pathogens encounter during infection, yet how bacteria respond to these immune-imposed conditions at the molecular level remains poorly understood. In this study, we profile the bacterial transcriptome directly in planta during infection with RNA-seq, providing a detailed view of pathogen responses under immune pressure. We focus on the previously identified two-component regulator CvsR and show that, despite widespread transcriptional changes induced by PTI, CvsR directly controls only a small core set of genes in planta. Instead, most bacterial transcriptional shifts reflect indirect responses to the immune-modified host environment. By capturing pathogen gene expression during infection, this work clarifies how plant immunity constrains bacterial physiology and provides insight that can inform sustainable strategies for crop protection.