CYP72A enzymes catalyse 13-hydrolyzation of gibberellins

Bioactive gibberellins (GAs or diterpenes) are essential hormones in land plants that control many aspects of plant growth and development. In flowering plants, 13-OH GAs (having low bioactivity—for example, GA 1 ) and 13-H GAs (having high bioactivity—for example, GA 4 ) frequently coexist in the same plant. However, the identity of the native Arabidopsis thaliana 13-hydroxylase GA and its physiological functions remain unknown. Here, we report that cytochrome P450 genes ( CYP72 A9 and its homologues) encode active GA 13-hydroxylases in Brassicaceae. Plants overexpressing CYP72A9 exhibited semi-dwarfism, which was caused by significant reduction in GA 4 levels. Biochemical assays revealed that recombinant CYP72A9 protein catalysed the conversion of 13-H GAs to the corresponding 13-OH GAs. CYP72A9 was expressed predominantly in developing seeds in Arabidopsis . Freshly harvested seeds of cyp72a9 mutants germinated more quickly than the wild type, whereas stratification-treated seeds and seeds from long-term storage did not. The evolutionary origin of GA 13-oxidases from the CYP72A subfamily was also investigated and discussed here.