When infiltrated at a higher concentration (108 cfu/ml), the gpsX mutant induced significantly less lesions than wild type at 7 dpi, but caused similar disease FK506 chemical structure symptoms as wild type at 14 dpi. In both cases, the complemented mutant strain with the intact gpsX cloned in pUFR053 showed no difference from the wild type strain (Figure 4A). Plant inoculation by spray, a method that mimics the natural infection, showed that the gpsX mutant was reduced in virulence on grapefruit compared with the wild-type strain 306. After 21 days post inoculation the number of canker lesions on leaves infected with the gpsX mutant was significantly less than that inoculated

with wild type strain. Symptom induction

by the gpsX mutant could be restored to the wild-type level by complementary plasmid pJU3110, but not by the empty vector (Figure 4B). Figure 4 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 see more 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. Although there were no differences between the wild type and the gpsX mutant strains Astemizole in the ability to grow in XVM2 medium (data not shown), the

growth of gpsX mutant 223 G4 (gpsX-) was significantly reduced in planta compared to the growth of the wild-type strain. After inoculation by infiltration at 105 cfu/ml, the bacterial population of the gpsX mutant moderately reduced in planta, and between 24 and 48 h, the bacterial population began to increase; whereas the bacterial population of the wild type strain 306 continued to increase after inoculation (Figure 5A). The bacterial population of the gpsX mutant recovered from the infected leaves was approximately 10 to 100-fold lower than that of the wild-type strain at each of the test points (Figure 5A). Similar differences in growth of the wild type and mutant strains were observed following infiltration at 108 cfu/ml (Figure 5B). The bacterial population of the complemented strain was similar to that of the wild-type at each test point (Figure 5A and 5B).