Functional analysis of the seed coat-specific gene GbMYB2 from cotton.

MYB transcription factors are essential for cotton fiber development. We isolated the R2R3-MYB gene GbMYB2 from Gossypium barbadense. RNA in situ hybridization analysis showed that GbMYB2 is mainly expressed in the outer integuments of cotton ovules and in elongating fibers. GbMYB2 expression increased throughout fiber initiation and during the elongation stage. The expression level of GbMYB2 was higher in the Gossypium hirsutum cultivar Xu142 than in the Xu142 (fl) mutant. Overexpression of GbMYB2 in Arabidopsis caused thicker leaf trichomes and longer roots to develop due to the activation of trichome development-related genes such as GL2. These results indicate that GbMYB2 is an R2R3-MYB gene that is involved in fiber development.