Functional analyses in the sugarcane - Leifsonia xyli subsp. xyli pathosystem: metabolic and cellular alterations in the host and responses to oxidative and osmotic stresses in the pathogen

Abstract

The aim o our research group is to understand the genesis of ratoon stunting (RSD), a disease of sugarcane caused by the bacterium Leifsonia xyli subsp. xyli (Lxx). Recent transcriptomic analysis of young plants infected by Lxx (Thematic Project 2008/56296-2) suggested that the differential expression during the development of the plant of genes involved in the regulation of the cell cycle and in the production of hormones is intimately associated with the genesis of RSD. However, since our analyses were done with young plants and the symptoms develop only in adult plants of the stubble (ratoon) crops, it was not possible to link the differential expression of these genes with the morphological alterations that result from the disease. Also, presently we do not know how these changes in gene expression translate into metabolic changes in the plant. Moreover, since we consider Lxx an endophyte with a dual behavior (parasitic/mutualistic) towards its host, our working hypothesis is that part of these changes might stimulate bacterial growth and that for this to happen the pathogen must cope with the stresses usually imposed by the host. Thus, the objectives of this proposal are to compare both the metabolic profiles of the leaves and of the xylem sap of plants from two varieties that differ in the degree of bacterial multiplication in their tissues and to compare the anatomy of meristematic cells of infected plants. In addition, the proposal explores the in vitro functionality of Lxx genes similar to bacterial genes involved in responses to oxidative and osmotic stresses. (AU)