Protein ubiquination in diploid parthenogenesis and early embryos of Norway spruce

• Published in: International journal of plant sciences Vol. 157; no. 1; pp. 17 - 26
• Main Author: Durzan, D.J. (University of California, Davis, CA.)
• Format: Journal Article
• Language: English
• Published: Chicago The University of Chicago Press 01-01-1996; University of Chicago, acting through its Press
• Subjects: Apoptosis; Botany; Cell nucleolus; Cell nucleus; CELLS; CELLULE; CELULAS; CHEMICAL REACTIONS; Cytoplasm; DEATH; DEGENERATION; Development; DIPLOIDIA; DIPLOIDIE; DIPLOIDY; EMBRIONES VEGETALES; EMBRYON VEGETAL; Embryos; Epidermal cells; Gels; IMMUNOCYTOCHEMISTRY; IMMUNOLOGIE; IMMUNOLOGY; INMUNOLOGIA; MORT; MUERTE; NOYAU CELLULAIRE; NUCLEI; NUCLEO; NUCLEOLE; NUCLEOLOS; NUCLEOLUS; NUCLEUS; PARTENOGENESIS; PARTHENOGENESE; PARTHENOGENESIS; Peroxisomes; PICEA ABIES; PLANT EMBRYOS; PLANT PROTEINS; Plant reproduction; programmed cell death; PROTEINAS; PROTEINE; PROTEINS; REACCIONES QUIMICAS; REACTION CHIMIQUE; Trees; UBIQUITIN; Ubiquitins
• ISSN: 1058-5893; 1537-5315
• DOI: 10.1086/297316

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 degrading nuclei and chromatin fibers. Proteins were color-coded by Stains-all as to their location in the axial tier and on SDS-PAGE gels for correlation with Western blots. Regulatory proteins from all cells along the tier were programmed for turnover. Ubiquinated, high-molecular-weight proteins in suspensors were released as mucilage into the culture medium. For viable early embryos, peroxisomes, which encode genes for the ubiquitin-conjugating protein family, accounted for the characteristic acetocarmine staining of the cytoplasm in the embryonal group.