Heterologous Expression of GbTCP4, a Class II TCP Transcription Factor, Regulates Trichome Formation and Root Hair Development in Arabidopsis.

Two class I family teosinte branched1/cycloidea/proliferating cell factor1 (TCP) proteins from allotetraploid cotton are involved in cotton fiber cell differentiation and elongation and root hair development. However, the biological function of most class II TCP proteins is unclear. This study sought to reveal the characteristics and functions of the sea-island cotton class II TCP gene by biochemical, genetic, and molecular biology methods. GbTCP4 protein localizes to nuclei, binding two types of TCP-binding -acting elements, including the one in its promoter. Expression pattern analysis revealed that is widely expressed in tissues, with the highest level in flowers. is expressed at different fiber development stages and has high transcription in fibers beginning at 5 days post anthesis (DPA). overexpression increases primary root hair length and density and leaf and stem trichomes in transgenic relative to wild-type plants (WT). GbTCP4 binds directly to the () promoter, increasing transcript levels in roots and reducing them in leaves. Compared with WT plants, lignin content in the stems of transgenic overexpressing increased, and gene transcript levels increased. These results suggest that GbTCP4 regulates trichome formation and root hair development in and may be a candidate gene for regulating cotton fiber elongation.