Protein Ubiquination in Diploid Parthenogenesis and Early Embryos of Norway Spruce

Abstract

Ontogenetically programmed cell death or apoptosis was initiated in individual nuclei by endonucleases and by the ubiquitin-mediated turnover of proteins. The salvage of degradation products ensured that a nutrient supply was available for survival of the developing embryos. In diploid parthenogenesis, the egg-equivalent nucleus underwent parthenogenesis and released proembryos from the egg cytoplasm as the egg cell was eliminated. Immunochemical evidence for the ubiquination of proteins was found mainly in nucleoli of viable cells in the proembryo, embryonal group of the early embryo, and throughout nuclei of abortive cells. During development of the axial tier of early embryos. the differentiation of embryonal suspensors was characterized by enucleation, nucleolar release, and by the processing of ubiquinated nuclear fragments by proteasome-like associations. Abortive early embryos, which comprised less than 5% of the population, underwent massive apoptosis giving a strong ubiquitin reactivity with degr...