The induction of hrp genes

in bacteria occurs soon after the first contact with plant tissue. Expression of hrp genes are detected as early as 1 h after inoculation and continue Selleckchem LY2603618 to increase for at least 6 h [6]. However, no specific plant-derivatives have been identified as inducers of hrp genes, and in Ralstonia solanacearum some evidence suggests that the full induction of hrp genes requires contact with plant tissues [7]. The hrp genes are also induced in vitro when bacteria are grown in minimal medium with carbon sources such as sucrose, fructose or mannitol, low pH and a low N/C ratio [6]. Minimal media with these characteristics seems to mimic some of the conditions bacteria might find AZD0156 molecular weight within the apoplast. It has been suggested that the induction of hrp genes after contact with plant tissues could result from alterations in the nutritional status of the bacteria [2, 6]. During the interaction with their host, it is thought that bacteria commonly detect specific plant metabolites, which are used as signals for changing their gene expression patterns, allowing them to adapt to the plant environment. Specific plant molecules such as phenolic β-glycosides, shikimic and quinic acids, and pectin oligomers

have been reported to Selleck Apoptosis Compound Library activate the expression of genes involved in toxin synthesis and cell wall degradation [8–10].

In this study, we used microarray analysis to identify genes of P. syringae pv. phaseolicola NPS3121 differentially expressed in response to metabolites present in plant tissue extracts [11]. Bacteria were grown on minimal medium supplemented with bean leaf extract, apoplastic fluid or bean pod extract. By using these three types of extract, we were able to identify Sucrase bacterial genes that possibly facilitate the colonization of susceptible plant tissues, such as bean leaves and/or apoplastic fluid which are known targets during the infection process of P. syringae pv. phaseolicola NPS3121 [11, 12]. Results and Discussion Leaf extracts and apoplastic fluid produce highly similar transcriptional responses We decided to test bean leaf and pod extracts and apoplastic fluid since these are thought to be the primary environments that P. syringae pv. phaseolicola encounters during infection, and in which nutrient assimilation, plant signal recognition and stress responses can occur [13, 14, 1, 12]. To this end, P. syringae pv. phaseolicola NPS3121 was grown at 18°C in M9 minimal medium with glucose as a carbon source. When cultures reached the mid-log phase (OD600 nm 0.6) bean leaf extract, apoplastic fluid or bean pod extracts were added to a final concentration of 2% and an equal amount of minimal medium was added to a control culture.