The full sequence of this plasmid is available on GenBank (accession number JN703735). Pspph1925 was PCR-amplified using the primers 1925compFw and 1925compRv (Supplementary Table 1) and directionally cloned into pSX via the introduced

NdeI and HindIII restriction sites. The accuracy of this and all other plasmid gene inserts was validated by sequencing (Macrogen, Korea). Targeted deletion of P. syringae 1448a genes Mutagenic plasmids were delivered to P. syringae 1448a using an electroporation protocol for Pseudomonas mutagenesis adapted from [38]. Overnight cultures were grown to stationary phase in LB media, then 6 ml of culture were aliquoted into 1.5 ml microfuge tubes for each electroporation. Cells were twice pelleted by centrifugation followed by resuspension Protein Tyrosine Kinase inhibitor in sterile 300 mM sucrose to wash. After the final wash all cells were pelleted, resuspended and pooled in 100 μl of 300 mM sucrose and transferred to a 2 mm gap electroporation cuvette together with 10 μl of mutagenic plasmid sample in ddH2O. Following electroporation

and recovery as described [66], GDC-941 100 μl samples were plated on LB containing chloramphenicol and rifampicin (P. syringae 1448a is rifampicin resistant; this antibiotic was added to avoid growth of contaminants, not for selection of pDM4 chromosomal integrants). Plates were then incubated for 48-72 h at 28°C. Subsequent selection of primary integrants and sacB counter-selection were performed as previously described [38], with the resulting colonies screened for desired mutation events by colony PCR. For pyoverdine NRPS knockouts, mutant genotypes were also confirmed by Southern blotting using an Amersham alkphos® kit with CDP Star® detection reagent according to the manufacturer’s instructions. CAS agar assays for iron uptake 100 ml Chromeazurol S (CAS) dye for the detection of siderophores

[67] was made by dissolving 60.5 mg CAS powder (Sigma) in 50 ml distilled water. To this 10 ml of a 1 mM solution of FeCl3 was added. The entire solution was then poured slowly with stirring into 40 ml distilled water containing 72.9 mg dissolved HDTMA (Sigma) and autoclaved to sterilize. To make agar plates, freshly autoclaved KB agar was cooled to 60°C before adding 1 part CAS dye to 9 parts media. Plates were immediately Inositol oxygenase poured, and at this point exhibited a dark green color. Strains were inoculated into dried CAS plates by picking a large colony with a sterile 100 μl pipette tip and piercing the tip approximately 5 mm into the 4SC-202 nmr surface of the agar plates. Plates were then incubated upside down at 28°C for 24 h. After 24 h incubation the 22°C condition was removed from the incubator and maintained at 22°C. Plates were photographed with minimal exposure to temperature change at 24, 48 and 72 h. The entire assay was repeated three times; results presented in figures are from a single assay and are representative of all repeats.