Comparative proteome analysis from Erwinia amylovora grown in vitro and in planta

Abstract

Fire blight, caused by the bacterium Erwinia amylovora, affects most species of the Malaceae and some species in other families of the Rosales. The severity of the disease results from its destructive character on the one hand and the lack of effective control methods on the other hand. To gain a better insight into the infection process and proteins involved, the proteome of bacteria grown in vitro and in planta (M9 kloon 29, apple rootstocks) was studied. After two-dimensional electrophoresis, differentially regulated protein spots were excised, trypsinized and analysed by LC-ESI-MS/MS. A total of 127 differentially expressed proteins were identified of which 108 are up-regulated in planta and 19 proteins are down-regulated. Most of the identified proteins ware involved in general metabolism; however, 26% are related to oxidative stress. Numerous defence mechanisms against oxidative stress are strongly up-regulated in bacteria in planta. The protective mechanisms can be divided into three groups: prevention of ROS generation, detoxification of radicals and repair of damaged elements. Our hypothesis is that these protective mechanisms are one of the strategies used by Erwinia amylovora to escape plant defence mechanisms.