Structural and Transcriptional Characterization of rbcS Genes of Cotton (Gossypium hirsutum)

Abstract

Ribulose bis-carboxylase/oxygenase small subunit genes (rbcS) are found to be highly expressed in most plant species. Promoters of rbcS genes have been isolated, characterized, and used to enhance expression of transgenes in transgenic lines. In this study, we have identified five different members of the rbcS gene family in cotton (Gossypium hirsutum). All five genes contain three exons and two introns. Nucleotide sequences of the rbcS genes are conserved in their coding regions, but exhibit considerable sequence divergence in both introns and in upstream and downstream flanking sequences. Based on sequence identity, these genes are grouped into two subfamilies. Promoters of all rbcS genes have been isolated, and their cis-acting motifs, exhibiting different arrangements, have been identified. All five rbcS genes are differentially expressed in leaf and boll tissues of cotton plants at different stages of plant development. Three of the five isolated rbcS genes are found to be highly expressed in analyzed tissues. Multiple transcriptional start sites of all members of the gene family have been identified in leaf and boll tissues of cotton plants. Moreover, different members of the rbcS gene family from the two progenitor diploid species of G. hirsutum, namely, Gossypium herbaceum and Gossypium raimondii, have also been isolated to identify the lineage of the five rbcS genes. In addition, a total of three candidate promoters that can be used to enhance expression of transgenes in cotton have been identified.