Figure 1.

Overexpression of ZmARGOS1 reduces ethylene responses in Arabidopsis plants. A, Bolting time is delayed in transgenic Arabidopsis plants overexpressing ZmARGOS1 relative to wild-type plants. Two 35S:ZmARGOS1 transgenic events (2B3 and 2C6) and wild-type (WT) controls were grown under a regime of 16 h of light (approximately 120 mE m⁻² s⁻¹) at 24°C and 8 h of darkness at 23°C. Means are shown for bolting time, days after planting (DAP). Error bars indicate sd; n = 18. Student’s t test was performed to compare the transgenic events and the wild-type control (*, P < 0.01). B, 35S:ZmARGOS1 Arabidopsis plants are insensitive to the ethylene precursor ACC. Seedlings were germinated in the dark in the presence or absence of 10 μm ACC for 3 d. Composite images of representative seedlings of 35S:ZmARGOS1 transgenic, etr1-1 mutant, and wild-type Columbia-0 (Col-0) plants are shown. C, Hypocotyl and root lengths of 3-d-old etiolated Arabidopsis seedlings. The triple response assay was conducted with 10 μm ACC. The data represent means of 10 to 20 seedlings from two 35S:ZmARGOS1 events (2B3 and 2C6), an etr1-1 mutant, and wild-type controls. Error bars indicate sd. Student’s t test was performed to compare the transgenic events and the etr1-1 mutant with the wild-type control (*, P < 0.01). D, Overexpression of ZmARGOS1 in the Arabidopsis eto1-1 mutant background. The 3-d-old, etiolated 35S:ZmARGOS1 eto1-1 seedlings lack the ethylene triple response phenotype in the absence of exogenously supplied ethylene. A composite image shows representative seedlings of wild-type plants and the transgenic Arabidopsis eto1-1 plants carrying ZmARGOS1 and empty vector. E, Hypocotyl and root lengths of etiolated Arabidopsis eto1-1 mutant plants overexpressing ZmARGOS1. Seeds were germinated under dark in the absence of exogenously supplied ethylene for 3 d. Three 35S:ZmARGOS1 events (ZmARGOS1 E1, E2, and E3) and three empty vector events (Vector E11, E12, and E13) in the eto1-1 mutant background are shown. Wild-type Arabidopsis and the eto1-1 mutant served as controls. The hypocotyls and roots in the 35S:ZmARGOS1 eto1-1 plants are significantly (*, P < 0.01) longer than those in the vector eto1-1 control events and the eto1-1 mutant. Error bars indicate sd; n = 20. F, Flowering time was delayed in the 35S:ZmARGOS1 eto1-1 Arabidopsis plants relative to the eto1-1 mutant. The delayed flowering time was observed in all 10 independent events tested. Representative 34-d-old transgenic eto1-1 plants carrying 35S:ZmARGOS1 and empty vector as well as the eto1-1 mutant plants are shown. Bar = 20 mm. G, ZmARGOS1(L104D), a mutated version of ZmARGOS1, was unable to confer ethylene insensitivity in Arabidopsis plants. Root and hypocotyl lengths were determined in transgenic Arabidopsis plants carrying empty vector, 35S:ZmARGOS1, and 35S:ZmARGOS1(L104D). Twelve T1 seeds per construct, each representing an independent event, were randomly selected based on the yellow fluorescent protein (YFP) marker and germinated in the dark in the presence or absence of 10 µm ACC. The means of the hypocotyl and root lengths are shown for 3-d-old seedlings. Error bars indicate sd. Student’s t test was performed to compare the transgenic events and empty vector controls (*, P < 0.01).