Figure 1.

Suppression of APY expression impairs R-induced hook opening, cotyledon expansion, and root growth. A, Apical hook opening of 3.5-day-old dark-grown seedlings, 2, 4, 6, 8, and 12 h after R treatment of WT Ws, (−E) R2-4A mutants without estradiol, and (+E) R2-4A mutants with estradiol. B, Increase in the growth of cotyledons of 2.5-day-old, etiolated seedlings induced by continuous R (30 mol m⁻² s⁻¹) is significantly inhibited in apy1 and apy2. Cotyledon area was measured at 24 h time intervals. C, Cotyledon area measurements with estradiol inducer added to R2-4A mutants at the beginning of the 3.5 days dark period and imaged 1, 2, and 3 days after R, (−E) R2-4A mutants without estradiol, and (+E) R2-4A mutants with estradiol. D, Root length measured at 24-h time intervals. Estradiol inducer was added to R2-4A mutants to suppress APY1 expression by RNAi after the 2.5 days dark period. E, Estradiol inducer is added to R2-4A mutants (+E) at the beginning of the 3.5 days dark period, maximal suppression of APY1 is evident when R treatment begins at the end of the dark period, and R does not induce any increase in primary root growth thereafter. For all panels (A–E), shown is a representative result that was observed in samples independently grown on three separate plates, each of which had an n value of at least 7, and different letters above the bars indicate values that differ significantly from each other (P < 0.05, Student’s t test, error bars are S.E.).