GhACE1 is a positive regulator promoting fiber elongation. A, RT-qPCR analysis of GhACE1 expression in fibers of the GhACE1 overexpression transgenic cotton lines (T2 generation). Total RNA was isolated from 9 DPA fibers of GhACE1 transgenic lines and WT. GhUBI1 (EU604080) was used as a quantification control. Error bars represent sd of three biological replicates. B, Mature fibers of GhACE1 overexpression transgenic cotton lines (T2 generation) and controls (WT and CK). Scale bar = 2 cm. C, Measurement and statistical analysis of mature fiber length of GhACE1 overexpression transgenic lines and controls (n ≥ 50 cotton ovules per line). D, GhACE1 overexpression transgenic ovules with fibers cultured in vitro. Cotton ovules (0 DPA) from GhACE1 overexpression transgenic lines and WT were in vitro cultured in liquid BT medium at 30°C in darkness for 12 d. Scale bar = 1 cm. E, Measurement and statistical analysis of the length of WT and transgenic fibers on ovules cultured in vitro for 12 d (n ≥ 50 cotton ovules per line). F, RT-qPCR analysis of expressions of fiber elongation-related genes in fibers of GhACE1 overexpression transgenic cotton plants. Total RNA was isolated from nine DPA fibers of GhACE1 transgenic lines and controls. GhUBI1 (EU604080) was used as a quantification control. Error bars represent sd of three biological replicates. Data in (A), (C), (E), and (F) were processed with Microsoft Excel, and error bars represent the sd. Independent t tests demonstrated significant (P < 0.05) or very significant (P < 0.01) difference between GhACE1 overexpression transgenic lines and WT. CK, the transgenic null line; AOE2-AOE11, GhACE1 overexpression transgenic cotton lines.