Major component of the RACK1 regulatory proteins that play a role in multiple signal transduction pathways. Involved in multiple hormone responses and developmental processes (PubMed:16829549, PubMed:18715992, PubMed:18947417). MAPK cascade scaffolding protein involved in the protease IV and ArgC signaling pathway but not the flg22 pathway (PubMed:25731164). Homodimer and heterodimer with RACK1B or RACK1C (Probable). Interacts with NUDT7 (PubMed:22068106). Interacts with GB1, MEKK1, MKK4, MKK5, MPK3 and MPK6, but not with GPA1 or MPK4 (PubMed:25731164). Interacts with OFUT20 (PubMed:23435172). Detected in the cytoplasm and nucleus when interacting with NUDT7. Widely expressed. Shorter hypocotyls in etiolated seedlings, epinastic cotyledons, reduced rosette leaf production by half and late flowering under short-day conditions. Reduced sensitivity to gibberellin and brassinosteroid in seed germination, hypersensitivity to abscisic acid in seed germination and early seedling development, and hyposensitivity to auxin in adventitious and lateral root formation. Plants show a significant resistance to water stress conditions by limiting water loss through the guard cells. Belongs to the WD repeat G protein beta family. Ribosomal protein RACK1 subfamily.