Figure 4.

Auxin Functions Downstream of PSK-PSKR1 Signaling in Tomato Immunity against B. cinerea.

(A) Changes in IAA content in PSK signaling component gene-silenced tomato plants. Leaf samples were collected at 0.5 dpi with B. cinerea.

(B) Effects of NAA application on leaf B. cinerea actin transcript abundance in target gene-silenced tomato plants at 1 dpi. PSK signaling component gene-silenced and TRV:0 control plants were treated with 50 nM NAA or water 12 h before B. cinerea inoculation.

(C) and (D) Immunity compromised by PSKR1 silencing was complemented by NAA but not by PSK.

(C) Trypan blue staining for cell death, as affected by PSKR1 silencing and application of PSK and NAA. Tomato PSKR1-silenced plants were treated with 10 µM PSK or 50 nM NAA 12 h before B. cinerea inoculation, and leaf samples were collected at 2 dpi. Bar = 250 µm.

(D) Relative B. cinerea actin transcript abundance in infected leaves at 1 dpi.

(E) The effects of 50 nM NAA application on the transcript abundance of PSK signaling component genes in tomato leaves under both mock- and B. cinerea-inoculated conditions. Samples were taken at 0.5 dpi.

The results in (A), (B), (D), and (E) are presented as mean values ± sd; n = 3 independent pooled samples with each sample being from two plants. Different letters indicate significant differences between treatments (P < 0.05, Tukey’s test). The experiments in (A), (B), and (E) were repeated three times, and others were repeated two times with similar results.