Isolation and expression profiles of gibberellin metabolism genes in developing male and female cones of Pinus tabuliformis

Gibberellins (GAs) are important in the floral regulatory networks of angiosperm plants. Several lines of evidence suggest that GAs also play a pivotal role in conifer male and female cone development. To gain new insights into the GA metabolism pathway in conifer trees and the role of GA metabolism in male and female cone development, we identified GA metabolism genes in Pinus tabuliformis. These included one PtCPS gene, one PtKS gene, one PtKO gene, TWO PtKAO genes, one PtGA20ox gene, two PtGA3ox genes and 12 PtGA2ox genes. According to phylogenetic analysis, the GA biosynthesis pathway evolved after the divergence of mosses from ferns, but the GA-deactivating gene family underwent divided expansion after divergence of the angiosperms from gymnosperms. However, the active sites of all GA metabolism enzymes were conserved during the evolution of land plants. During male and female cone development of P. tabuliformis, the expression of most of the PtGA2ox genes, especially PtGA2ox10, was higher than GA biosynthesis genes. However, the expression of PtKAO1 in cones peaked at a very early developmental stage. The expression pattern of GA metabolism genes indicated that GAs play different roles at the early and late stages of cone development.