citri colonization of the phyllosphere, which may be due, at least partly,

to the role of T3SS in X. citri biofilm formation. Figure 4 Analysis of T3SS gene expression in leaf-associated grown X. citri and survival of X. citri , hrp mutants and hrpB − c cells associated to leaves. (A) RT-qPCR to determine hrpG, hrpX and hrpE expression levels in X. citri grown associated to leaves. Bars indicate the expression levels of the T3SS genes at two days of leaf-associated growth relative to time 0. Values are the means of four biological replicates with three ABT-263 price technical replicates each. (B) X. citri, hrp mutants and hrpB −c strains leaf-associated survival on citrus leaves. Values represent an average of four leaves assayed for each strain. Error bars indicate the standard deviation. Proteomic analysis of statically cultured X. citri and hrpB − strains In order to gain new insights about the role of T3SS in biofilm formation, a proteomic analysis was performed to identify differentially expressed selleck chemicals proteins between X. citri and the hrpB − mutant grown statically. A total of 49 differentially expressed protein spots were detected of which 32 were up- and 17 down-regulated in the hrpB- mutant

in comparison to X. citri (Table 1). Identified proteins were used to determine enriched GO categories in biological processes and molecular function. The main enriched categories for the up- and down-regulated proteins with an average fold change of minimum ± 1.5 and p value < 0.05 BIRB 796 in the hrpB − mutant relative to X. citri were represented graphically

(Figure 5). The categories that showed a major enrichment unless in the up-regulated proteins in the hrpB- mutant include ‘metabolic process’, ‘catabolic process’, ‘biosynthetic process’ and ‘generation of precursor metabolites and energy’. Moreover, ‘cell cycle’, ‘cellular homeostasis’ and ‘cellular process’ were categories enriched in up-regulated proteins in this mutant. Most of the identified proteins in the categories of ‘transporter activity’ or ‘receptor activity’ belong to different classes of outer membrane proteins (OMPs) such as: FadL (XAC0019), that allows the passage of fatty acids [26], OmpW (XAC3664), involved in the transport of small hydrophilic molecules across the bacterial outer membrane [27] and RpfN (XAC2504), which was reported to play a role in carbohydrate transport [28]. In these categories also several TonB-dependent transporters (TBDTs), which are outer membrane transporters involved in the active uptake and/or in signal transduction [29], as well as two Oar (OmpA-related) proteins were detected as differentially expressed between the two strains. Table 1 Differentially expressed protein spots between X. citri and hrpB − strains statically cultured in XVM2 with a change abundance of minimum 1.5 fold and p value of < 0.05 (ANOVA) X. citri gene no. Protein name MOWSE score Accession no.