Genomic analyses of the crosstalk between gibberellins and brassinosteroids metabolisms in tea plant (Camellia sinensis (L.) O. Kuntze)

Endogenous phytohormones gibberellins (GAs) and brassinosteroids (BRs) are associated with the development and growth of higher plants, but the crosstalk between them in leaves of tea plant is unclear. We determined whether or not a crosstalk exists between GAs and BRs at three developmental stages of tea leaves. We performed phytohormone measurement, phenotypic analysis, cytological-anatomical structural analysis, RT-qPCR analysis, and protein-protein interaction (PPI) prediction to obtain physiological, biochemical, and bioinformatic evidences. Leaf area, spongy tissue cell expansion, and GAs- and BRs-related gene expressions were regulated by the crosstalk between GAs and BRs. GAs levels positively correlated with BRs levels at three developmental stages of tea leaves. GAs levels positively correlated with the expression levels of CsCPD (Cytochrome P450 90A1) and CsDWF4 (Dwarf4), which are involved in BRs biosynthesis pathway at three developmental stages of tea leaves. The expression of CsGA20ox1 (Gibberellin 20 oxidase 1), a gene involved in the GAs biosynthesis pathway, positively correlated with GAs and BRs levels at three developmental stages of tea leaves. These results suggested that CsGA20ox1, CsCPD, and CsDWF4 might play regulative roles in the crosstalk between GAs and BRs at the developmental stages of tea leaves. Our findings provided a new and feasible strategy to understand the crosstalk between the GAs and BRs metabolism pathways.