Transcription activator that binds DNA on 5'-ACTCTAC-3' and promotes auxin homeostasis-regulating gene expression (e.g. YUC genes), as well as genes affecting stamen development, cell expansion and timing of flowering. Synergistically with other SHI-related proteins, regulates gynoecium, stamen and leaf development in a dose-dependent manner, controlling apical-basal patterning. Promotes style and stigma formation, and influence vascular development during gynoecium development. May also have a role in the formation and/or maintenance of the shoot apical meristem (SAM). Modulates root growth. Homodimer. Restricted to lateral root primordia. Expressed during the early stages of root primordium development and disappears prior to the emergence of lateral roots from the parent root. Expression repressed by LDL1 via histone H3 and H4 deacetylation. No visible phenotype. Belongs to the SHI protein family.