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. 2020 Jul 30;10(1):12862.
doi: 10.1038/s41598-020-69627-2.

Coronatine is more potent than jasmonates in regulating Arabidopsis circadian clock

Min Gao  1 , Chong Zhang  1   2 , Hua Lu  3
Affiliations

Coronatine is more potent than jasmonates in regulating Arabidopsis circadian clock

Min Gao et al. Sci Rep. .

Abstract

Recent studies establish a crucial role of the circadian clock in regulating plant defense against pathogens. Whether pathogens modulate host circadian clock as a potential strategy to suppress host innate immunity is not well understood. Coronatine is a toxin produced by the bacterial pathogen Pseudomonas syringae that is known to counteract Arabidopsis defense through mimicking defense signaling molecules, jasmonates (JAs). We report here that COR preferentially suppresses expression of clock-related genes in high throughput gene expression studies, compared with the plant-derived JA molecule methyl jasmonate (MJ). COR treatment dampens the amplitude and lengthens the period of all four reporters tested while MJ and another JA agonist JA-isoleucine (JA-Ile) only affect some reporters. COR, MJ, and JA-Ile act through the canonical JA receptor COI1 in clock regulation. These data support a stronger role of the pathogen-derived molecule COR than plant-derived JA molecules in regulating Arabidopsis clock. Further study shall reveal mechanisms underlying COR regulation of host circadian clock.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
COR exerts stronger suppression on expression of circadian genes than MJ. (A) Heatmap analysis of expression of circadian genes in MJ-treated samples. (B) Heatmap analysis of expression of circadian genes in COR-treated samples. For (A) and (B), Log2 transformed fold change of gene expression (100 µM MJ or 5 µM COR treatment vs. mock treatment) was used to generate the heatmaps with the heatmap.2 function in R package gplots. For MJ treatment, the mock solution contained 0.015% (v/v) Silwet L77 and 0.1% ethanol. For COR treatment, water was used as a mock treatment. (C) Relative number of genes affected by MJ or COR. Expression of each gene at a time point was considered as one gene expression event. The total number of defense or clock gene expression events in each category was normalized by the total number of time points.
Figure 2
Figure 2
COR treatment affects clock activity. LD-entrained 5 days old seedlings were transferred to LL for 1 day and were treated with COR or water at 25 h (top of each panel) or 37 h (bottom of each panel). Luminescence was recorded at 1 h intervals for 5 days and analyzed for clock activity. (A1)–(D1) Expression of CCA1:LUC in Col-0. (A2)–(D2) Expression of TOC1:LUC in Col-0. (A3)–(D3) Expression of PRR7:LUC in Col-0. (A4)-(D4) Expression of GRP7:LUC in Col-0. (A5)-(D5) Expression of CCA1:LUC in coi-17. (A1)–(A5) Luminescence traces. RLU relative luminescence units. The color indicates COR concentration, black for 0, magenta for 1 µM, and gray for 10 µM. (B1)–(B5) Normalized amplitude. The amplitude of the reporter was normalized to the relative leaf area shown in Figure S5. (C1)–(C5) Period. (D1)–(D5) Phase shift. Data represent mean ± SEM (n = 12). Statistical analysis was performed by One-way ANOVA post-hoc Tukey HSD test. Different letters indicate significant difference among the samples (P < 0.05). These experiments were repeated three times with similar results.
Figure 3
Figure 3
MJ treatment affects clock activity. LD-entrained 5 days old seedlings were transferred to LL for 1 day and were treated with MJ or water at 25 h (top of each panel) or 37 h (bottom of each panel). Luminescence was recorded at 1-h intervals for 5 days and analyzed for clock activity. (A1)–(D1) Expression of TOC1:LUC in Col-0. (A2)-(D2) Expression of PRR7:LUC in Col-0. (A3)–(D3) Expression of GRP7:LUC in Col-0. (A1)–(A3) Luminescence traces. RLU relative luminescence units. The color indicates MJ concentration, black for 0, magenta for 10 µM, and gray for 100 µM. (B1)-(B3) Normalized amplitude. The amplitude of the reporter was normalized to the relative leaf area shown in Figure S5. (C1)–(C3) Period. (D1)–(D3) Phase shift. Data represent mean ± SEM (n = 12). Statistical analysis was performed by One-way ANOVA post-hoc Tukey HSD test. Different letters indicate significant difference among the samples (P < 0.05). These experiments were repeated three times with similar results.
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