Figure 5. Enhanced ethylene-response in mhz4 coleoptiles is rescued by ABA and MHZ4 mutation leads to ethylene overproduction.

(A) ABA rescue of enhanced ethylene-response phenotype in mhz4 coleoptiles. WT and mhz4 seedlings were grown in the dark for 2.5 d in the absence or presence of 10 ppm ethylene, with or without supplementation of 0.1 µM ABA. Bar = 10 mm. (B) Quantification of coleoptile growth with treatments in (A). Each column is average of 30 seedlings and bars indicate SD. ** indicates significant difference between the linked two samples at P<0.01. (C) Ethylene production in WT and mhz4 mutant. Data are the mean ± SD of three replicates. ** indicate significant difference compared to WT at P<0.01. (D) Expression of ethylene biosynthetic genes in 3 d-old etiolated seedlings of WT and mhz4. (E) Ethylene dose-response curves for coleoptile elongation in WT and mhz4 seedlings in the presence or absence of 5 µM of ethylene biosynthesis inhibitor AVG. Dark grown seedlings were treated with various concentrations of ethylene for 2.5 d. Each point is average of 25 to 30 seedlings and bars indicate SD. (F) Coleoptile elongation phenotypes of WT and mhz4 in the presence or absence of 5 µM of AVG. The ethylene concentration was 10 ppm. Others are as in (E). Bar = 10 mm. (G) OsEIN2 gene expression in WT and mhz4 etiolated seedlings detected by semiquantitative RT-PCR. Rice seedlings were grown in the dark for 3 days and RNA was isolated from the shoots and roots. Actin1 was used as an internal control.