<i>WRKY33</i> functions downstream of the MPK3/MPK6 cascade in inducing the expression of <i>ACS2</i> and <i>ACS6</i> genes in the gain-of-function <i>DD</i> seedlings.

<p>(A) Mutation of <i>WRKY33</i> compromises ethylene induction in <i>DD</i> seedlings. Twelve-day-old <i>DD</i> and <i>DD/wrky33</i> seedlings grown in GC vials were treated with 1-µM DEX. Ethylene accumulation in GC vials was monitored at indicated times, and then seedlings were collected for gene expression analysis. Error bars indicate standard deviations (n = 3). (B) MPK3/MPK6-induced <i>ACS2</i> and <i>ACS6</i> gene expression in <i>DD</i> plants is dependent on <i>WRKY33</i>. Total RNA was extracted from seedlings collected in (A). Expressions of <i>ACS2</i> (upper panel) and <i>ACS6</i> (lower panel) genes were quantified by real-time PCR. <i>ACS</i> transcript levels were calculated as a percentage of the <i>EF1α</i> transcript. Error bars indicate standard deviations (n = 3).