Abstract.When artichoke tuber tissue was cultured in mineral salts, the induction of DNA synthesis and subsequent cell division was dependent upon the presence of auxin in the incubation medium. Evidence is provided that an obligatory set of metabolic events precedes auxin‐induced DNA synthesis, and previous work has associated these with protein synthesis. As a consequence the auxin‐induced changes in nuclear and cytoplasmic proteins have been investigated. Using 2D gel electrophoresis, qualitative alterations in nuclear non‐histone proteins have been detected from the earliest treatment times with auxin. These changes were progressive, starting with four novel proteins after 3 h auxin treatment and ending with about forty when DNA synthesis commences some 18–21 h later. Qualitative alterations in phosphorylated nuclear proteins due to auxin treatment were only detectable when DNA synthesis commenced. In contrast, few qualitative alterations in cytoplasmic proteins were detectable, with the major change being in phosphorylated proteins at the onset of DNA synthesis.A possible model of auxin action is outlined which involves sequential and progressive changes in the synthesis of nuclear proteins and the control of gene expression eventually leading to DNA sy