Characterization of genes responsive to osmotic and oxidative stresses of the sugarcane bacterial pathogen Leifsonia xyli subsp. xyli.

Leifsonia xyli subsp. xyli (Lxx) colonizes the xylem vessels of sugarcane, a plant niche where microorganisms are highly exposed to oxidative and osmotic stresses. This study performed an in silico analysis of the genome of Lxx and characterized 16 genes related to the detoxification of oxidative species (peroxidases, O2- dismutases, and methionine reductases) and to the production and transport of osmolytes and analyzed their expression in vitro after 30, 60, and 120 min of exposure to H2O2 or PEG. The PAGE activity of superoxide dismutase (Mn-SOD as confirmed by inhibition tests) and of catalase (CAT) and the accumulation of trehalose were also assessed. Exposure to H2O2 increased the expression of most oxidative-responsive genes and decreased the expression of those related to osmotic responses, whereas the opposite occurred after exposure to PEG. The isoform profiles of CAT and Mn-SOD shifted in response to H2O2 but not to PEG and Lxx cells accumulated more trehalose over time after exposure to PEG compared with non-exposed cells. The experimental results validated the in silico analysis and indicated that this obligate endophytic parasite has multiple and functional mechanisms to combat the stresses imposed by its host.