Auxin controls rice root angle via kinase OsILA1-mediated cell wall modifications

Auxin-mediated root gravitropism critically determines root angle, a key trait that underpins root system architecture (RSA). Auxin response factors (ARFs) regulate this process, but their downstream targets and functions remain unclear. We demonstrate that OsARF12 and OsARF25 induce cell wall thickness in epidermal cells of the lower side of the root, positioning auxin as a “break” of these cells during gravistimulation by directly regulating Increased Leaf Angle1 ( OsILA1 ) through a dual set of auxin response elements. Our study therefore establishes a direct link between auxin transcriptional signaling and cell wall fortification, driving the differential cell elongation required for root gravitropism and angle.