Promotes pollen tube growth (PubMed:15255864, PubMed:24938288). A C-terminal peptide is cleaved from the propeptide in the stigmatic exudate and represent the major form of STIG1 (PubMed:24938288). Binds phosphoinositol lipids (PubMed:24938288). The binding of external phosphatidylinositol 3-phosphate (PI(3)P) and PRK2 by STIG1 induces a rapid intracellular reactive oxygen species elevation (PubMed:24938288). Interacts with PRK1 and PRK2 (via extracellular domain). Expressed in the stigma and the upper section of the style. Belongs to the STIG1 family.