A genome-wide identification of the BLH gene family reveals BLH1 involved in cotton fiber development

Cotton is the world’s largest and most important source of renewable natural fiber. BEL1-like homeodomain (BLH) genes are ubiquitous in plants and have been reported to contribute to plant development. However, there is no comprehensive characterization of this gene family in cotton. In this study, 32, 16, and 18 BLH genes were identified from the G. hirsutum, G. arboreum, and G. raimondii genome, respectively. In addition, we also studied the phylogenetic relationships, chromosomal location, gene structure, and gene expression patterns of the BLH genes. The results indicated that these BLH proteins were divided into seven distinct groups by phylogenetic analysis. Among them, 25 members were assigned to 15 chromosomes. Furthermore, gene structure, chromosomal location, conserved motifs, and expression level of BLH genes were investigated in G. hirsutum. Expression profiles analysis showed that four genes (GhBLH1_3, GhBLH1_4, GhBLH1_5, and GhBLH1_6) from BLH1 subfamily were highly expressed during the fiber cell elongation period. The expression levels of these genes were significantly induced by gibberellic acid and brassinosteroid, but not auxin. Exogenous application of gibberellic acid significantly enhanced GhBLH1_3, GhBLH1_4, and GhBLH1_5 transcripts. Expression levels of GhBLH1_3 and GhBLH1_4 genes were significantly increased under brassinosteroid treatment. The BLH gene family plays a very important role in many biological processes during plant growth and development. This study deepens our understanding of the role of the GhBLH1 gene involved in fiber development and will help us in breeding better cotton varieties in the future.