Temperature-Mediated Differential Gene Expression in Plant Pathogenic Bacteria

Abstract

Plant pathogenic bacteria cause numerous devastating diseases in worldwide important crops thereby drawing increasing attention to the improved understanding of their infection processes. Phytopathogens, like our model organism, the gram-negative bacterium Pseudomonas syringae, encounter a number of environmental signals during the course of infection of their respective host plants. Foliar plant pathogens causing leaf spot diseases depend on high humidity and the proper temperature conditions to successfully infect the host plant, to rapidly overcome plant defense mechanisms, and to establish in planta population sizes which allow intense disease development. For many P. syringae pathovars high humidity and low temperatures have been shown to foster disease outcome. In analogy to human and animal pathogens that recognize the interior of their respective host organisms by a number of environmental signals, P. syringae might detect the proper conditions for bacterial infection and survival in its host plants. With respect to temperature it has been well established that human and animal pathogenic bacteria express virulence factors at 37–40°C but not at 25–30°C. It has been proposed that by means of temperature regulation - these pathogens economize gene expression: The bacteria synthesize virulence factors preferably at the time point and location when and where they are actually needed - in the interior of the warm-blooded host.