Fig 1.
Observation of plant damage after exposure of Arabidopsis plants to N2O5 gas.
The N2O5 gas exposure time for each plant is shown in the lower left corner. Observations were made before, immediately after, 6 h after, 24 h after, and 4 days after N2O5 gas exposure. Magnified images at 4 days after some of the N2O5 gas exposure times (0 s, 30 s, 40 s, and 5 min) are shown in the lower right corner. Red arrowheads indicate a leaf that turned brown immediately after the N2O5 gas exposure. Yellow arrowheads indicated the location of leaves that were damaged by the N2O5 gas. Scale bar is 2 cm.
Fig 2.
Induction of Botrytis cinerea resistance in Arabidopsis plants by N2O5 gas exposure.
(A) Arabidopsis plants exposed to N2O5 gas were inoculated with B. cinerea. Scale bar is 1 cm. (B) Areas of the lesions at 2 days after B. cinerea inoculation were measured and the mean (± standard deviation) is shown. Different letters indicate significant differences according to the Tukey–Kramer test (n = 11–12, P < 0.05).
Fig 3.
Response of N2O5-gas-exposed Arabidopsis plants to infection with Pseudomonas syringae pv. tomato DC3000.
(A) Lesion formation was observed at 3 days after Pst inoculation. Red arrows indicate inoculated leaves. Scale bar indicates 1 cm. (B) Inoculated leaves were collected at 2 days after infection and the bacterial titer (cfu/mg fresh weight of leaf material) was determine by the colony counting method. The graph shows means (± standard deviation) of the results from three independent plants. No significant differences between the treatments were detected (Student’s t-test, P < 0.05). (C) Plant biomass and bacterial biomass were calculated by qPCR and the ratio of bacterial DNA per plant DNA was shown. There were no significant differences between treatments at each time point (Student’s t-test, n = 3, P < 0.05).
Fig 4.
Induction of cucumber mosaic virus resistance in Arabidopsis plants by N2O5 gas exposure.
Arabidopsis plants exposed to N2O5 gas were inoculated with CMV(Y). Two days after inoculation, the inoculated leaves were harvested and subjected to enzyme-linked immunosorbent assay using an antibody against the CMV CP. Asterisks denote significant differences (Student’s t-test, n = 6, P < 0.05).
Fig 5.
Changes in the expression of genes related to plant disease defense responses over time after exposure of Arabidopsis plants to N2O5 gas.
The mRNA transcript abundances of genes related to plant disease defense, including WRKY25, WRKY26, WRKY33, PEN2, CYP71A13, PAD3, ORA59, and PDF1.2, were analyzed using qRT-PCR. Asterisks denote significant differences to 0 h samples (without N2O5 gas exposure; Dunnett’s test, n = 3, P < 0.05). ACT2, ACTIN2.
Fig 6.
Expression of defense-related genes in coi1-1 and ein2-1 mutant Arabidopsis plants after exposure to N2O5 gas.
The accumulation of mRNA transcripts of defense-related genes, including WRKY33, PAD3, ORA59, and PDF1.2 was analyzed in wild-type, coi1-1, and ein2-1 Arabidopsis plants. Different letters denote significant differences among treatments (Tukey–Kramer test, n = 3, P < 0.05). ACT2, ACTIN2.
Fig 7.
Resistance induced by N2O5-gas against Botrytis cinerea and CMV in Arabidopsis phytohormone signaling mutants.
(A) The areas of the lesions at 2 days after B. cinerea inoculation were measured and the mean (± standard deviation) is shown. Asterisks denote significant differences (Student’s t-test, n = 9, P < 0.05). (B) Two days after CMV(Y) inoculation, the inoculated leaves were harvested and subjected to ELISA. Asterisks denote significant differences (Student’s t-test, n = 6, P < 0.05). n.s.: not significant.