Mediates responses to the synthetic auxin 2,4-dichlorophenoxyacetic acid (2,4-D). Not involved in the response to indole-3-acetic acid (IAA). Interacts with RUB modification-related components and may regulate the cullin-ring ubiquitin E3 ligase complex (CRL) activity. Interacts with the COP9 signalosome. Expressed in roots, flowers, siliques, stems, leaves and seeds. In flowers, detected in petals, anthers and pistils. The F/D-rich region (45-62) is necessary but not sufficient for SMAP1 function. No visible phenotype, except a longer hypocotyl in light-grown seedlings.