Figure 1.

GA biosynthesis in bacteria. (a) GA biosynthetic operon. The core operon (CYP112 → KS) is mostly conserved, while other genes such as CYP115 and IDI (isopentenyl diphosphate δ-isomerase) are only present in certain strains. Additionally, the core GA operon found in most rhizobia contains a 5′ CYP115 fragment, and most full-length CYP115 in rhizobia, when present, are followed by a 3′ CYP112 fragment. (b) GA biosynthesis in core operon containing rhizobia ends at GA₉ (1) with C-3β hydroxylation of GA₉ by a GA3ox required to produce the bioactive GA₄ (2).