However, changes were observed in the effector proteins HopAK1 and HopAT1 that could be attributed to the presence of specific signal molecules in both the leaf extract and the apoplast fluid. It has been demonstrated that type III effector proteins are translocated through the TTSS directly into the cytosol of the host cell, where they interfere with or modulate host cell processes to facilitate bacterial multiplication, invasion and disease [24–26]. Genes encoding pectin lyase and polygalacturonase were also up-regulated (Figure 5). Previous studies demonstrated that pectin lyase and polygalacturonase are both induced in plant tissues or in vitro cultures that contain plant extracts [27,

28, 4, 22]. Both, pectin lyase and polygalacturonase are Doramapimod cost involved in pectin degradation, and possibly facilitate the assembly of functional type III secretion complexes [29–31]. In TH-302 mouse P. syringae strains, pectin lyase, polygalacturonase and type III effector proteins with a pectate lyase domain, Ilomastat in vitro such as HopAK1, are found in some pathovars, however little is known about their role and contribution to pathogenicity [32–35]. The four genes discussed above show a hrp box motif in their regulatory region; this element is recognized or bound by HrpL, an alternative RNA

polymerase sigma factor that regulates the expression of many genes involved in pathogenesis and virulence [36, 4]. Thus, if this group of genes is transcribed by a common sigma factor, it makes sense that it is found to be up-regulated under these conditions. However RT-PCR analysis showed that hrpL is also expressed in M9 without plant extracts therefore some possibilities are that an additional regulator is necessary to activate these genes or some anti-sigma could be inactivated in this precise condition. Definitively more studies

are necessary to find the mechanism of transcription of this group of genes by HrpL (Figure 5). In addition, 17-DMAG (Alvespimycin) HCl cluster I contains a gene that encodes a protein with a secretin N-domain that is closely related to bacterial type II and III secretion system proteins, which export proteins from within the bacterial cell to the extracellular matrix and/or into target host cells [25]. Leaf extract also induces a gene encoding a protein with a phytase domain, most likely involved in the hydrolysis of the phytate present in the bean leaf extract [37–39]. Figure 5 Functional analysis of the results of microarray profiles. Red and green letters represent induced and repressed genes respectively. Gray words represent genes constitutively expressed under our study conditions (name of genes or their identifiers are in parenthesis). We propose that induction of some genes is related to the presence of host components in the medium (leaf and apoplast). Similarly, repression of genes involved in iron acquisition, suggests that host extracts are a non-limiting source of this element.