Inhibition of flowering by gibberellins in the woody plant Jatropha curcas is restored by overexpression of JcFT

Jatropha curcas is a perennial oil-seed plant with vigorous vegetative growth but relatively poor reproductive growth and low seed yield. Gibberellins (GA) promote flowering in most annual plants, but inhibit flower initiation in many woody plants, including J. curcas. However, the underlying mechanisms of GA inhibition on flowering in perennial woody plants remain unclear. Here, we found that overexpression of the gibberellin biosynthesis gene JcGA20ox1 delays flowering in J. curcas and in the J. curcas × J. integerrima hybrids. Consistent with this finding, overexpression of the GA catabolic gene JcGA2ox6 induces early flowering in J. curcas. qRTPCR revealed that the inhibition of floral transition by overexpressing JcGA20ox1 resulted from the decreased of JcFT and other flowering related genes, which was restored by overexpressing JcFT in J. curcas. Overexpression of JcGA20ox1 or JcGA2ox6 reduced seed yield, but overexpression of JcFT significantly increased seed yield. Furthermore, hybridization experiments showed that the reduction in seed yield caused by overexpression of JcGA20ox1 or JcGA2ox6 was partially restored by the overexpression of JcFT. In addition, JcGA20ox1, JcGA2ox6 and JcFT were also found to be involved in the regulation of seed oil content and endosperm development. In conclusion, our study revealed the inhibitiory effect of GA on flowering in J. curcas is mediated through JcFT and demonstratd the effects of JcGA20ox1, JcGA2ox6 and JcFT on agronomic traits. This study also indicates the potential value of GA metabolism genes and JcFT in breeding new varieties of woody oil-seed plants.