Plant bodies are built from immobile cells, making the regulation of cell expansion essential for growth, development, and adaptation. In roots, cell elongation executes the movement of the root tips through the soil. This process is tightly controlled by numerous signaling pathways. Among these, gibberellin and auxin signaling stand out for their contrasting effects on root growth, interacting through complex cross talk at multiple regulatory levels. Here, we reveal the molecular basis of the auxin-gibberellin cross talk in the model plant Arabidopsis thaliana. We show that the auxin signaling pathway steers the expression of GIBBERELLIN 2-OXIDASES (GA2OXs), key gibberellin-deactivating enzymes in the root elongation zone (EZ). GA2OXs are negative regulators of root cell elongation; GA2OX8 overexpression decreases gibberellin levels and inhibits root cell elongation; in contrast, the ga2ox heptuple mutant roots show elevated gibberellin levels in the EZ and grow longer roots. Intriguingly, shoot-derived auxin can regulate GA2OX6 and GA2OX8 expression in roots, linking systemic auxin signaling to local gibberellin level modulation. Together, our findings identify GA2OX6 and GA2OX8 enzymes as key mediators of auxin-gibberellin cross talk, providing insights into their roles in root elongation. These results expand our understanding of how auxin integrates with gibberellin signaling to coordinate root development and growth dynamics.

• Keywords
• Arabidopsis, auxin, gibberellin, root,
• MeSH
• Arabidopsis * growth & development   metabolism   genetics   enzymology   MeSH
• Gibberellins * metabolism   MeSH
• Plant Roots * growth & development   metabolism   genetics   MeSH
• Indoleacetic Acids * metabolism   MeSH
• Mixed Function Oxygenases * metabolism   genetics   MeSH
• Arabidopsis Proteins * metabolism   genetics   MeSH
• Gene Expression Regulation, Plant MeSH
• Plant Growth Regulators metabolism   MeSH
• Signal Transduction MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• gibberellin 2-dioxygenase MeSH Browser
• Gibberellins * MeSH
• Indoleacetic Acids * MeSH
• Mixed Function Oxygenases * MeSH
• Arabidopsis Proteins * MeSH
• Plant Growth Regulators MeSH