Involvement of STH7 in light-adapted development in Arabidopsis thaliana promoted by both strigolactone and karrikin

Figures & data

Fig. 1. Strigolactone and karrikin inhibit the hypocotyl length of 4-day-old wild-type Arabidopsis under weak light conditions.

Notes: Response of various concentrations of GR24 (A, C) and KAR₁ (B, D) on hypocotyl elongation. Data are means ± SD shown by vertical error bars (n ≥ 17). Means with the same letter are not significantly different at p ≤ 0.05 according to Tukey–Kramer’s honestly significant difference test. The scale bars represent 10 mm.

Fig. 2. Quantitative RT-PCR analysis of STH7 expression level.

Notes: Relative transcript levels of STH7 in wild-type Arabidopsis treated with 0.1% (v/v) DMSO as a control, 10 μM GR24 or 10 μM KAR₁ (A); relative transcript levels of STH7 in various STH7-ox and STH7-SRDX mutant lines (B). Plants were grown in 1/2 MS medium under weak light conditions for 4 days. The transcript levels were normalized to those of ACT7. Data are means ± SD shown by vertical error bars (n = 3). Standard deviations are shown as vertical error bars. Statistically significant differences relative to the control are **p ≤ 0.01 and *p ≤ 0.05 by Student’s t test.

Fig. 3. Phenotype of STH7-ox and STH7-SRDX mutants.

Notes: Hypocotyl length at 7 days old under light conditions (A); petiole length at 14 and 21 days old under light conditions (B); 7-day-old seedlings, scale bars represent 1 mm (C); 21-day-old plants, scale bars represent 10 mm (D). Data are means ± SD shown by vertical error bars (n ≥ 28). Means with the same letter are not significantly different at p ≤ 0.05 according to Tukey–Kramer’s honestly significant difference test.

Fig. 4. Strigolactone and karrikin decrease hypocotyl elongation of STH7-ox depending on their concentrations.

Notes: Effect of GR24 (A) and KAR₁ (B) on 4-day-old hypocotyl elongation of wild-type Arabidopsis, STH7-ox, and STH7-SRDX mutants under weak light conditions. All data are means ± SD shown by vertical error bars (n ≥ 18). Statistically significant differences relative to each control are **p ≤ 0.01, *p ≤ 0.05, and ns: non-significant by Student’s t test.

Fig. 5. Response of strigolactone and karrikin on hypocotyl elongation.

Notes: Comparison of hypocotyl elongation in wild-type Arabidopsis ecotype Col, max2-1, and max3-1 mutants (A); comparison of hypocotyl elongation in wild-type Arabidopsis ecotype Col and Ler, d14-1, and kai2 mutants (B). Plants were treated with 0.1% DMSO as control, 10 μM GR24 or 10 μM KAR₁. Data are means ± SD shown by vertical error bars (n ≥ 18). Statistically significant differences relative to each control are **p ≤ 0.01, *p ≤ 0.05, and ns: non-significant by Student’s t-test.

Fig. 6. Anthocyanin (A), total chlorophyll (B), chlorophyll a (C), and chlorophyll b (D) content in various STH7-ox and STH7-SRDX mutant lines.

Notes: Plants were grown under darkness for 7 days and exposed to light for 6 or 12 h to de-etiolate. Data are means ± SD shown by vertical error bars (n ≥ 3). Means with the same letter are not significantly different at p ≤ 0.05 according to Tukey–Kramer’s honestly significant difference test.

Fig. 7. Effect of strigolactone and karrikin on anthocyanin content.

Notes: Wild-type Arabidopsis, STH7-ox, and STH7-SRDX mutants were grown in medium containing 0.1% DMSO as control, 10 μM GR24 or 10 μM KAR₁ under light conditions for 7 days. Data are means ± SD shown by vertical error bars (n ≥ 3). Statistically significant differences relative to each control are **p ≤ 0.01, *p ≤ 0.05, and ns: non-significant by Student’s t test.

Fig. 8. Quantitative RT-PCR analysis of photosynthesis-related gene expression.

Notes: Relative transcript levels of LHCB1 (A), rbcS (B), and CHS (C) in wild-type Arabidopsis, STH7-ox, and STH7-SRDX mutants. Plants were grown in 1/2 MS medium under darkness for 4 days and incubated in 0.1% (v/v) DMSO as a control, 10 μM GR24 or 10 μM KAR₁ solution for 3 h. Data are means ± SD shown by vertical error bars (n = 3). Means with the same letter are not significantly different at p ≤ 0.05 according to Tukey–Kramer’s honestly significant difference test.

Fig. 9. Working model of strigolactone (SL) and karrikin (KAR) effects on light-adapted development or photomorphogenesis.

Notes: Strigolactone regulates light-adapted growth mediated by D14 and KAI2 while karrikin response is mediated by only KAI2. MAX2 is important for both strigolactone and karrikin signaling in light-adapted development in an STH7-dependent manner. Strigolactone and karrikin induce photomorphogenesis by the inhibition of hypocotyl elongation, the increase of anthocyanin and chlorophyll content and the up-regulation of photosynthesis-related genes. Dashed-line arrows indicate that unnatural SL can perceive in this way.