Acts as a scaffold, mediating interaction of ROPs with different proteins. Required for primary and adventitious root maintenance, but not for their formation. Promotes the stabilization of ARAC11 on the plasma membrane of the pollen tube initiation site but not the activation of ARAC11. Regulates directionality of polar auxin transport, and is required for the formation of a stable auxin maximum and tip localized auxin gradient during embryogenesis, organogenesis, and meristem activity. Involved in exocytosis and in the recycling of PIN proteins back to the plasma membrane. Homooligomer. Interacts with ARAC3, ARAC4, ARAC8, ARAC11 and SEC3A, but not with ICR2 or EXO70A1. The localization of the ICR1-ROP complexes at the plasma membrane depend on the lipid modifications of the ROPs (PubMed:17493810). Localized in the nuclei in mature pollen, then shifts to the site of germination and stays at the apical cortex of growing pollen tubes (PubMed:19825600). Expressed in mature and germinating pollen (PubMed:19825600). Expressed throughout the embryo but not in the hypophysis and quiescent center (QC). In roots, absent from the QC and the stem cells (PubMed:20098722). Up-regulated by auxin. Interactions with ROPs and SEC3A require an intact C-terminal coiled-coil domain. Plants have cubical adaxial epidermal pavement cells and show a loss of root stem-cell population due to a colapse of the root meristem. Pollen development is also compromised. Belongs to the ICR family.