FIG 6.

Both DksA and ppGpp activate T3SS gene expression in Erwinia amylovora. (A) Expression of T3SS regulatory and effector genes (hrpL, hrpA, hrpN, and dspE) in the relA, spoT, dksA, relA/dksA, and relA/spoT (ppGpp⁰) mutant strains compared to the WT strain in HMM, as determined by qRT-PCR. (B) Expression of T3SS regulatory and effector genes (hrpL, hrpA, hrpN, and dspE) in the relA, spoT, dksA, relA/dksA, and ppGpp⁰ mutant strains compared to the WT on immature pear fruits. Relative gene expression of selected T3SS genes was calculated by the 2^−ΔΔCT method, utilizing the rpoD gene as an endogenous control. Fold changes are the means of results for three replicates. Each experiment was performed at least two times with similar results. Error bars indicated standard deviations.