Cloning and expression of GhTM6, a gene that encodes a B-class MADS-box protein in Gossypium hirsutum

A full-length cDNA designated GhTM6, which encodes an organ differentiation-related B-class MADS-box protein, was isolated from Upland cotton (Gossipium hirsutum) by screening a normalized fulllength cDNA library and using a RT-PCR strategy. The translated sequence analysis indicated that the polypeptide contained MADS-box and K domains and had a classic TM6 motif, i.e., the paleoAP3 in the C-terminal region. The phylogenetic analysis showed that GhTM6 is closest to CeTM6, MaTM6, BuTM6, and PhTM6. Quantitative RT-PCR analysis showed that the GhTM6 gene was expressed at high levels in all tissues examined, such as those from squares, flowers, petals, stamens, and carpels under normal growth conditions. GhTM6 was expressed at high levels before floral initiation and declined thereafter. Furthermore, six stamens were seen in the transgenic tobacco flower as compared to five stamens in a wild-type flower. The results indicated that GhTM6 did not exhibit the full B-function spectrum, because it is only involved in the determination of stamen organ identity. However, its function in cotton will need to be examined in transgenic cotton plants.