Indole-3-Butyric Acid (IBA) Derivatives for Root Architecture Modulation: Potent Promoters via In Vivo Conversion to...

Area of Science:

• Plant Biology
• Biochemistry
• Organic Chemistry

Background:

• Indole-3-butyric acid (IBA) is a key plant hormone regulating root development.
• High concentrations of IBA can inhibit primary root elongation, limiting its application.
• Novel IBA derivatives are needed to enhance root architecture without adverse effects.

Purpose of the Study:

• To investigate the effects of novel IBA-derived compounds, JAX-44 and JAX-77, on plant root architecture.
• To elucidate the metabolic pathway and mechanism of action of JAX-44 and JAX-77 in vivo.
• To explore the structure-activity relationship of IBA derivatives in modulating root development.

Main Methods:

• Synthesis and application of IBA derivatives (JAX-44, JAX-77, JAX-86, JAX-83).
• Root growth assays in *Arabidopsis thaliana* to assess effects on primary, lateral, and adventitious roots.
• Mass spectrometry and metabolic analysis to determine in vivo conversion pathways.

Main Results:

• JAX-44 and JAX-77 significantly promote lateral and adventitious root formation while maintaining primary root length.
• JAX-44 is converted in vivo to IBA via JAX-77, involving oxidative decarbonylation.
• N- or O-methylation (JAX-86, JAX-83) abolishes promotion and induces selective lateral root inhibition.
• The N-unsubstituted indole structure is critical for the activation pathway.

Conclusions:

• JAX-44 and JAX-77 represent advanced plant growth regulators with improved efficacy and flexibility for root system optimization.
• These compounds serve as valuable tools for understanding auxin biology and the structural basis of IBA activity.
• The findings highlight the potential for designing novel auxin analogs with tailored biological effects.