Figure 4

Expression levels of possible common targets of PthA2, PthA4 and/or PthC1. (A) Expression levels of the Avr9/Cf9-elicited 146 (AE146) and UDPGT genes in response to TAL effector expression in citrus epicotyls. Although binding sites for PthA2, PthA4 and PthC1 were identified in the AE146 gene promoter, AE146 is strongly induced by PthA2 and 4 only. The UDPGT gene, which was down-regulated by PthA2 in microarray experiments, and has a predicted PthA2-binding site in its promoter, is repressed by all three effector proteins. (B) Expression levels of two citrus LOB genes (LOB1 and LOB2) in response to TAL effector expression in citrus epicotyls. LOB1, identified as a target of PthA4 and PthC1 was preferentially modulated by these effectors, whereas LOB2, identified as a PthA2 target by EBE prediction is apparently up-regulated by all three effectors. The expression levels are the mean of three independent biological replicates. The error bars denote standard deviations whereas asterisks indicate statistically significant differences (p < 0.05) in the mRNA levels in epicotyls expressing the TAL effectors relative to GUS.