Computational and Biochemical Analysis of the Xanthomonas Effector AvrBs2 and Its Role in the Modulation of Xanthomonas Type Three Effector Delivery
Figure 5
Bs2 activation by AvrBs2 blocks TTSS delivery of two independent effector reporters to host cells.
The TTSS effector delivery reporter constructs consisted of the effector promoter and the secretion and translocation signal peptide translationally fused to adenylate cyclase (Cya). These constructs were introduced into Xe in tandem with the native effector by single homologous recombination. Pepper (no R genes), pepper (Bs1) and pepper (Bs2) were sampled 8 hours post-inoculation to avoid in planta multiplication of the reporter strain pairs (with and without AvrBs2) and assayed for cyclic AMP (cAMP). TTSS delivered effector-Cya translational fusions into the plant cell and calmodulin from the plant cell leads to elevated levels of cAMP. A. AvrBs11-212-Cya reporter in strains Xe (avrBs2 and avrBs1) and Xe (avrBs1) were inoculated into pepper plants (no R genes, Bs1 or Bs2). In planta cAMP levels were assayed. Student t-test was used to compare TTSS delivery of effector reporter in an Xe strain with and without avrBs2 on Pepper (+) Bs2; p-values were <0.05. B. XopX1-183-Cya reporter in strains Xe (avrBs2 and avrBs1) and Xe (avrBs1) were inoculated into pepper plants (no R genes, Bs1 or Bs2). In planta cAMP levels were assayed. Student t-test was used to compare TTSS delivery of effector reporter in an Xe strain with and without avrBs2 on Pepper (+) Bs2; p-values were <0.01.