Figure 8.

HD2A and HD2C decrease H3K9 acetylation level and coregulate root growth via GA2ox-mediated GA catabolism. (A-C) Western blots and relative intensities of H3K9ac/H3 in hd2 mutants (A), HD2A-OE (B), and HD2C-OE (C) lines. The fold changes in the relative intensities of H3K9ac/H3 were normalized to WT. The intensities of blotting signals were quantified using Image J software. Data shown are means ± standard errors (n = 3) from three independent experiments. The significance of the differences between different genotypes was determined by one-way ANOVA followed by post-hoc Tukey’s HSD tests (A) and Student’s t test (B-C). Lowercase letters or asterisks indicate significant differences at p < 0.01. (D-G) Relative expression of GA2ox1 and GA2ox2 genes in hd2 mutants (D), HD2A-OE (E), and HD2C-OE (F) lines in 10-day old seedlings under control conditions. (G) Relative expression of GA2ox1 and GA2ox2 genes in WT under control, ABA (100 µM), and PEG-6000 conditions. Data shown are means ± standard errors (n = 3) from three independent experiments. The significance of the differences between different genotypes in (D) was determined by one-way ANOVA followed by post-hoc Tukey’s HSD tests. The significance of the differences between different genotypes in (E-G) was determined by Student’s t test. Lowercase letters indicate significant differences at p < 0.01, whereas asterisks indicate significant differences at *p < 0.05, **p < 0.01. (H, I) Primary root lengths measured in 10-day old WT, hd2a, hd2c, and Mac16 seedlings under GA4 (1 µM and 10 µM) (H) and GA3 (1 µM and 10 µM) (I) treatments. Data shown are means ± standard errors (n = 60). Three independent experiments were performed in this test. In each experiment, 20 seedlings of each genotype were used to measure the primary root lengths. The significance of the differences between different genotypes was determined by one-way ANOVA followed by post-hoc Tukey’s HSD tests. Lowercase letters indicate significant differences (p < 0.01).