Spatiotemporal interplay between cAMP-CRP and KdgR regulates virulence in Pectobacterium carotovorum.
TL;DR
A sophisticated spatiotemporal program where the interplay between cAMP-CRP and KdgR prioritizes motility at nutrient-depleted regions for outward expansion while sustaining PCWDE production across the lesion to maximize tissue maceration is highlighted.
Abstract
Phytopathogens encounter highly heterogeneous environments during infection. Carbon availability is a fundamental metabolic constraint that impacts bacterial virulence; however, the mechanism underlying the coordination of virulence traits based on metabolic cues remains unclear. We investigated the regulatory network of the soft-rot pathogen Pectobacterium carotovorum during Napa cabbage colonization, which generates tissue maceration with steep glucose and pectin gradients. Using GFP transcriptional fusions, we mapped the spatiotemporal expression of key regulatory (flhD, rsmA, and rsmB) and functional (fliC and pelA) virulence genes across necrotic lesions. As disease progressed, glucose and pectin accumulated at lesion centers before dissipating, establishing a distinct chemical zonation that mirrored virulence-gene profiles. Flagellar genes and rsmA showed consistent upregulation at lesion margins via the glucose-responsive cAMP-CRP system. In contrast, rsmB was upregulated at both centers and margins, whereas plant cell wall-degrading enzymes (PCWDEs) maintained relatively uniform expression. This spatial differentiation was driven by the concerted action of cAMP-CRP and pectin-responsive KdgR. cAMP-CRP disruption but not that of KdgR abolished the spatial organization of virulence gene expression and impaired lesion expansion, underscoring its central role in infection dynamics. Additionally, identification of previously unrecognized CRP-dependent targets reveals its expanded regulatory scope in Pectobacterium. These findings indicate a sophisticated spatiotemporal program where the interplay between cAMP-CRP and KdgR prioritizes motility at nutrient-depleted regions for outward expansion while sustaining PCWDE production across the lesion to maximize tissue maceration. This study highlights how carbon-responsive networks enable pathogens to exploit the complex chemical landscape of host tissues.