Changes in Protein Synthesis upon Cytokinin-Mediated Adventitious Bud Induction and during Seedling Development in Norway Spruce, Picea abies

A pulse-treatment of embryos of Picea abies (L.) Karst with cytokinin efficiently and reproducibly induces the coordinate de novo formation of bud primordia from subepidermal cells. The cytokinin treatment also affects the germinative development of the embryo; chloroplast maturation is delayed, and cell elongation is completely suppressed. We have analyzed the protein patterns in developing spruce embryos with the aim of identifying proteins which are differentially synthesized during early bud-differentiation and germination. In addition to a set of major seed storage proteins and a large set of constitutively synthesized proteins, we distinguish two sets of proteins that showed different patterns of synthesis in relation to germination. One was synthesized at high rates during germination, and the second set during post-germinative seedling development. Twenty-two proteins were differentially synthesized in the bud-induced versus the germinating embryos. Interestingly, all 22 belonged to either the germination phase-abundant or the seedling protein sets, whereas the constitutively synthesized proteins were unaffected by the treatment. Proteins synthesized exclusively in bud-induced embryos were not found. In total, the bud-induction treatment caused a maintenance of a protein synthesis pattern typical for the germination phase in the nontreated embryos, and the de novo formation of buds was not preceded by a major change in gene expression in the tissue.