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). Expressed in seedlings, roots, cauline leaves, flowers and siliques. Expressed in the apical parts of the developing gynoecium. In carpels, first observed at late development stage in the most apical parts of the open-ended gynoecium. Accumulates in differentiating style and stigmatic tissues. Not expressed in the stigma after fertilization but remains in the style until full silique maturation. Also detected in anthers. In seedlings, present in the shoot apex and in cotyledons, leaf primordia, stipules, hydathodes and in primordia of lateral roots. Detected in developing trichomes and in leaf and pedicel attachment sites. No visible phenotype. The double mutant sty1-1 and sty2-1 has a reduction in the amount of stylar and stigmatic tissues and decreased proliferation of stylar xylem, as well as shorter siliques and rosette and cauline leaves with a higher degree of serration. Hypersensitive to 1-N-naphthylphtalamic acid (NPA), but restored by exogenous application of auxin. Belongs to the SHI protein family.