GpsX is important for host virulence of X. citri subsp. citri. (A) Suspensions of each strain [approximately 105 and 108 cfu/ml, respectively] were inoculated into the intercellular spaces of fully expanded, immature grapefruit (C. paradise cv. Duncan) leaves by pressure infiltration with a needleless syringe. A representative leaf from four replicates was photographed at 7 and 14 dpi, respectively. W: wild-type strain 306; M: gpsX mutant 223 G4 (gpsX-); MV: gpsX mutant 223G4V (gpsX-) with empty vector pUFR053; CM: complemented gpsX mutant C223G4 (gpsX+). (B) Bacterial cell suspensions (approximately 108 cfu/ml) of wild-type strain 306 and its derivatives were inoculated onto fully expanded, immature grapefruit by spray. Images are representative of five independent replicates at 21 dpi.