Fig. 5: Submergence affects histone modifications.

a Genomic structure of the OPR3 gene. Black boxes, exons; white boxes, untranslated regions. Sequence elements used for ChIP assays are annotated as P1 to P7. b, c Histone modifications at OPR3 locus. Ten-day-old Col-0 seedlings were submerged for 1 h and then transferred to the air. Re-aerated seedlings were wounded immediately and harvested 1 h after the treatment. Anti-H3K4me2 (b) and anti-H3Ac (c) antibodies were used for immunoprecipitation. Three to four biological replicates were averaged. Error bars indicate ±SD. Letters indicate groups that are statistically significantly different from each other (P < 0.05, Tukey’s test). It is noteworthy that the data were statistically analysed separately for individual sequence elements by one-way ANOVA. Individual data points were marked in IP. IP, immunoprecipitation; NC, negative control. d Effects of TSA on wound-induced gene expressions after submergence. The Col-0 seedlings grown on DMSO- or TSA-containing MS-agar media were submerged for 1 h and then transferred to the air. Re-aerated seedlings were wounded and harvested at the indicated time points after the treatment. Three biological replicates were averaged. Letters indicate groups that are statistically significantly different from each other (P < 0.01, Tukey’s test). Error bars indicate ±SD. It is noteworthy that DMSO is used for mock treatment. e Schematic model for wound-induced defence responses after the submergence. In the ambient air, wounding induces expression of JA biosynthesis genes for defence against herbivores. When plants undergo submergence, ethylene signalling was activated and histone modifications were changed from the active to inactive states. There would be other unknown regulators (X) activated by submergence to inhibit wound responses. These events would block wound-induced gene expressions, resulting in reduced herbivore resistance.