Isolation and characterization of full-length coding sequences of gibberellic acid biosynthetic genes in coconut (Cocos nucifera L.) and their expression analysis

Abstract

Gibberellic acid (GA) is intricately associated with plant growth and developmental pathways. To elucidate GA metabolism in coconut, we cloned full-length coding regions of the seven GA biosynthetic pathway genes (CPS, KS, KO, KAO, GA20ox, GA3ox and GA2ox) using a comparative genomics approach, using sequences from oil palm and date palm. The predicted amino acid sequences of the seven coconut GA biosynthetic genes shared high identities with oil palm and date palm GA biosynthetic genes. In silico structural and functional analyses were performed, and secondary and tertiary structures were predicted. Compared to the other two palms, the evolutionary analysis of the seven genes in coconut revealed that these genes may not be evolving rapidly enough to keep pace with occurring mutations. Additionally, we performed expression profiling of these seven genes during germination of mature zygotic embryos under in vitro conditions in two phenotypically contrasting coconut accessions (West Coast Tall and Chowghat Green Dwarf) and in response to exogenously supplemented GA3 and paclobutrazol (PBZ) in the embryo culture medium. While PBZ had an antagonistic effect on the GA biosynthesis pathway, GA3 enhanced the overall GA production. These results provide the first insights into GA biosynthesis in coconut, laying the foundation for future studies to decipher the genetics of dwarfism in coconut.