Characterization and expression of a putative retinoblastoma protein binding gene from Gossypium hirsutum

A genomic clone representing a putative retinoblastoma binding (RBB) protein was isolated from a Gossypium hirsutum BAC library. Alignment of the gene sequence with the cDNA sequence indicated the gene consists of six exons that have standard eukaryotic splice junctions. The conceptual spliced transcript was 98% identical to TC37171 in the TIGR gene index, however it encoded an ORF 107 amino acids longer than best deduced protein from TC37171. The conceptual translation of the genomic clone was 56% identical to a tomato gene experimentally demonstrated to be a RBB protein and able to complement the yeast growth mutant IRA. The mRNA encoded by the genomic clone was abundantly expressed in meristems and expression levels increased as the cotton fiber matured. We propose that this gene may regulate growth and/or cell division in cotton based on homology of the clone with a protein of known function and sites of expression.