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.

• Klíčová slova
• Arabidopsis, auxin, gibberellin, root,
• MeSH
• Arabidopsis * růst a vývoj   metabolismus   genetika   enzymologie   MeSH
• gibereliny * metabolismus   MeSH
• kořeny rostlin * růst a vývoj   metabolismus   genetika   MeSH
• kyseliny indoloctové * metabolismus   MeSH
• oxygenasy se smíšenou funkcí * metabolismus   genetika   MeSH
• proteiny huseníčku * metabolismus   genetika   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin metabolismus   MeSH
• signální transdukce MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• gibberellin 2-dioxygenase MeSH Prohlížeč
• gibereliny * MeSH
• kyseliny indoloctové * MeSH
• oxygenasy se smíšenou funkcí * MeSH
• proteiny huseníčku * MeSH
• regulátory růstu rostlin MeSH

Aux/IAA proteins are well-known as key components of the nuclear auxin signaling pathway, repressing gene transcription when present and enabling gene activation upon their degradation. In this review, we explore the additional roles of Aux/IAA proteins in the known auxin perception pathways-the TIR1/AFBs nuclear as well as in the emerging cytoplasmic and apoplastic pathways. We summarize recent advances in understanding the regulation of Aux/IAA protein stability at the post-translational level, a critical factor in auxin-regulated transcriptional output. We further highlight the roles of auxin-nondegradable non-canonical Aux/IAAs in auxin-mediated transcription and their involvement in apoplastic auxin signalling. Additionally, we discuss the importance of Aux/IAAs for the adenylate cyclase activity of TIR1/AFB receptors and speculate on their involvement in the cytoplasmic auxin pathway. Using Arabidopsis root as a model, this work underscores the central role of Aux/IAA proteins in mediating auxin-driven developmental processes and environmental responses. Key questions for future research are proposed to further unravel the dynamic roles of Aux/IAAs in auxin signaling networks.

• MeSH
• Arabidopsis * metabolismus   genetika   MeSH
• F-box proteiny metabolismus   genetika   MeSH
• kořeny rostlin metabolismus   MeSH
• kyseliny indoloctové * metabolismus   MeSH
• proteiny huseníčku * metabolismus   genetika   MeSH
• receptory buněčného povrchu metabolismus   genetika   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin * metabolismus   MeSH
• rostlinné proteiny * metabolismus   genetika   MeSH
• signální transdukce MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• F-box proteiny MeSH
• kyseliny indoloctové * MeSH
• proteiny huseníčku * MeSH
• receptory buněčného povrchu MeSH
• regulátory růstu rostlin * MeSH
• rostlinné proteiny * MeSH