Labeling Studies Clarify the Committed Step in Bacterial Gibberellin Biosynthesis

Area of Science:

• Biochemistry
• Plant Science
• Microbiology

Background:

• Gibberellins are crucial plant hormones regulating growth and development.
• Bacterial gibberellin biosynthesis pathways have been identified but remain incompletely understood.
• The evolution of phytohormone biosynthesis in bacteria presents a unique area of study.

Purpose of the Study:

• To elucidate the mechanism of the
• B
• ring contraction in bacterial gibberellin biosynthesis.
• To investigate the role of cytochrome P450 (CYP114) in this key biosynthetic step.
• To compare the bacterial mechanism with known pathways in plants and fungi.

Main Methods:

• ¹³C-labeling experiments to trace metabolic pathways.
• Nuclear Magnetic Resonance (NMR) spectroscopy for structural and mechanistic analysis.
• Enzymatic assays using purified cytochrome P450 (CYP114).

Main Results:

• The committed step in bacterial gibberellin biosynthesis involves a cytochrome P450 (CYP114).
• CYP114 catalyzes an unusual
• B
• ring contraction via oxidative extrusion of carbon-7 from ent-kaurenoic acid.
• This bacterial transformation is chemically identical to the convergently evolved process in plants and fungi.

Conclusions:

• Bacterial gibberellin biosynthesis utilizes a mechanism similar to that in plants and fungi, indicating convergent evolution.
• A shared semipinacol rearrangement mechanism, potentially influenced by carbon-4α carboxylate proximity, is proposed for this
• B
• ring contraction.
• This finding deepens our understanding of hormone biosynthesis evolution across different kingdoms.