Figure 1.
Necrosis symptoms in Nicotiana benthamiana leaves infiltrated with Xanthomonas oryzae pv. oryzae (Xoo) and a hrcU mutant.
Suspension of Xoo YN-1 and a hrcU mutant (ΔhrcU) at 8×107 cfu/ml was infiltrated into right and left half of leaves of N. benthamiana plants, respectively. Symptoms at 0, 12, 24 and 48 hours post infiltration (hpi) were shown.
Figure 2.
Strong H2O2 accumulation in Xoo-infiltrated area prior to formation of hypersensitive necrosis.
Leaves that were infiltrated with Xoo (right half) and hrcU mutant (left half) suspension were sampled sequentially at different time-points. H2O2 in leaves was detected by diaminobenzidine (DAB) staining analysis, and appeared as brown deposit. Bar = 20 µm.
Figure 3.
Upregulation of HR- and defense-related genes in Xoo-infiltrated leaves.
Gene expression was analyzed by qRT-PCR with gene specific primers. HR marker genes HIN1 and HSR203J, a pivatol defense regulator NPR1 and a set of PR genes were analyzed for their expression in Xoo-infiltrated plants at 12 hpi and 24 hpi.
Figure 4.
Population dynamics of Xoo inside the plant leaf tissues after infiltration.
Cell numbers of Xoo in the infiltrated leaf tissues were determined based on calculation of colony-forming units of the sampled tissues.
Table 1.
Effect of silencing of seven ACE genes on Xoo-induced HR in N. benthamian.
Figure 5.
Effect of silencing of seven ACE genes on Xoo-induced HR (A) and Cf-4-dependent HR (B) in N. benthamiana.
HR assays was performed three weeks after agroinfiltration. Control vector (CV, containing a fragment of eGFP gene in pTRV2)-agroinfiltrated plants were used as control plants. Photographs were taken at 3 dpi.
Table 2.
PCR primers used in this study.
Figure 6.
Efficiency of ACE gene silencing in N. benthamiana plants.
Gene silencing efficiency was evaluated with the change of transcript abundance of genes for silence three weeks after agroinfiltration in silencing-treated plants in comparison with that in CV-treated control plants. Transcript abundance of target genes was analyzed by qRT-PCR. A 18s rDNA gene was also analyzed as inner loading control.
Figure 7.
Effect of ACE95 and ACE35 gene silencing on nonhost resistance to Xoo in N. benthamiana plants.
Bacterial cell numbers of Xoo in the infiltrated leaf tissues of ACE95- and ACE35-silenced plants and CV control plants was determined based on calculation of colony-forming units of the sampled tissues.
Table 3.
Effect of silencing of seven ACE genes on Cf-4/Avr4-dependent HR in N. benthamian.
Table 4.
Annotation of the seven ACE genes required for HR and nonhost resistance to Xoo and/or Cf-4/Avr4-dependent HR.