Expression of the ferrioxamine receptor gene of Erwinia amylovora CFBP 1430 during pathogenesis

Mutants of Erwinia amylovora CFBP 1430 lacking a functional high-affinity i ron transport system mediated by desferrioxamine are impaired in their abil ity to initiate fire blight symptoms (A, Dellagi, M.-N. Brisset, J.-P. Paul in, and D. Expert. Mol. Plant-Microbe Interact. 11:734-742, 1998), In this study, a chromosomal transcriptional lacZ fusion was used to analyze the ex pression in planta of the E. amylovora ferrioxamine receptor gene foxR. Lac Z activity produced by the strain harboring the fusion was highly induced i n iron-restricted conditions and in inoculated apple leaf tissues, Microsco pic observation revealed differential expression of this gene in relation t o the localization and density of bacterial cells within the diseased tissu e. Thus, the ability of bacterial cells to express their iron transport sys tem in accordance with environmental conditions is likely important for dis ease evolution.