Homeobox Protein 24 Mediates the Conversion of Indole-3-Butyric Acid to Indole-3-Acetic Acid to Promote Root Hair Elongation

The study investigated the role of HOMEOBOX PROTEIN 24 (HB24) in promoting root hair elongation in Arabidopsis thaliana by mediating the conversion of indole-3-butyric acid (IBA) to indole-3-acetic acid (IAA). HB24 was found to regulate the expression of the IBR1 gene, essential for this conversion, and acted as a transcriptional activator by binding to the IBR1 promoter. Loss-of-function mutants of HB24 and IBR1 exhibited shorter root hairs, while overexpression of HB24 resulted in longer root hairs. The study demonstrated a feedback loop where IAA increased HB24 expression, further enhancing root hair growth. This research provided insights into the molecular mechanisms of root hair development and the role of HB24 in auxin signaling pathways.