Molecular Cloning and Characterization of a Novel Gossypium barbadense L. RAD-Like Gene

Abstract

Cotton fiber development is controlled by MYB family transcription factors. Here, we identify a SANT/MYB transcription factor from Gossypium barbadens, designated as \GbRL1. The full-length cDNA of GbRL1 contains an open-reading frame of 243 bp, encoding a protein of 81 amino acids with a calculated molecular mass of 9.32 kDa and an isoelectric point of 6.72. Sequence alignment shows that GbRL1 has high homology with other single SANT/MYB domain-containing genes, especially the RADIALIS (RAD) genes in Antirrhinum majus and Bournea leiophylla. Expression analysis reveals that at the seedling stage, GbRL1 is strongly expressed in roots but weakly in leaves and stamens. In 0-day post-anthesis (DPA) flowers, the expression of GbRL1 is strong in the petals and ovules, moderate in stamens. In ovules, during early fiber development, GbRL1 has high expression level at fiber initiation stage (−3 and 0 DPA) but low level at fiber elongation stage (3, 5, and 8 DPA). In addition, we also detect the expression of GbRL1 in elongating fibers (8 DPA). Promoter analysis indicates that the expression of GbRL1 may be controlled by genes involved in flower organ development and flowering time control, such as AGAMOUS-like genes and FLC gene. The overexpression of GbRL1 in Arabidopsis causes similar developmental alterations as overexpression of RAD. Together, our results suggest that GbRL1 may not only control flower development as RAD, but also plays an important role in early ovule development and/or fiber initiation in cotton.