Figure 2.

Ethylene signaling negatively regulates WDL4 expression during hook development. A, RT-qPCR analysis of WDL4 transcript levels in 3-day-old etiolated WT seedlings grown on half-strength MS medium alone (mock) or treated with 100 µM ACC for 4 h. Values represent mean ± sd for three individual biological repeats (**P < 0.01). B, RT-qPCR analysis of WDL4 transcript levels in 3-day-old etiolated seedlings of WT, the eto1-1 mutant, the EIN3ox transgenic line, and the ein3 eil1 mutant. Values represent mean ± sd for three individual biological repeats (*P < 0.05, **P < 0.01). C, Representative images of GUS staining in the hook region of WDL4pro:GUS transgenic seedlings in medium (mock) or with 10  µM ACC treatment. Seedlings were stained and imaged after growth in the dark for 3 days. D, Representative images of GUS staining in the hook region of WDL4pro:GUS transgenic seedlings in medium without (control) or with the indicated chemicals, the ethylene receptor antagonist AgNO₃ and the ethylene biosynthesis inhibitor AVG. Seedlings were stained and imaged after growth in the dark for 1 or 2 days. E, Representative images of GUS staining in the hook region of WDL4pro:GUS transgenic ein3 eil1 seedlings. Two independent lines were checked after seedling growth in the dark for 1 or 2 days. Scale bar = 0.2 mm.