Cytological study of some chromatin bound enzymes in Allium cepa L. by in vitro autoradiography

Payne, Jeremiah Frederick (1975) Cytological study of some chromatin bound enzymes in Allium cepa L. by in vitro autoradiography. Doctoral (PhD) thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (39MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

Autoradiography has been used with tritiated precursors to cytologically demonstrate in vitro nuclear RNA polymerase, DAN polymerase, poly(ADP-ribose) polymerase and RNA methylase in frozen sections of plant tissue (Allium cepa L. cultivar white Barletta). DNA polymerase, poly(ADP-ribose) polymerase and RNA methylase have been cytologically established for the first time (from any tissue source). This is also the first report of the presence of poly(ADP-ribose) polymerase in higher plants. -- Different RNA polymerase activities can be reliably demonstrated in cytologic sections. Both nucleolar and nucleoplasmic RNA polymerases appear preformed in onion seed and bulb root tissues. Nucleolar and nucleoplasmic activity is observed in the endosperm from the beginning of hydration while in the embryo axis, distinct nucleolar activity is preceded by general nucleoplasmic labeling. Both nucleolar and nucleoplasmic polymerases were fund in bulb roots before sprouting. -- No G2 cells were found in the ungerminated seed, while a small population occurred in the bulb roots. Rare occurrence of S phase nuclei and mitotic figures indicated that slow growth is maintained in the bulb roots and the G2 cells do not represent a ‘true’ physiologically blocked population. Ultrastructural studies substantiated possible slow growth and (or) degenerative changes in the roots of stored bulbs. -- DNA polymerase activity can be adequately retained in apparent S phase nuclei of root meristems. A low level of activity was demonstrated in the ungerminated seed in the apparent absence of de novo protein synthesis. -- Nuclei in storage cotyledonary cells, in contrast to other tissues, were not efficient templates for exogenous DNA polymerase. -- In vitro amino acid incorporation in cytologic sections was decreased with unlabelled precursors and polyuridylic acid, but not with protein synthesis inhibitors. -- RNA methylase activity was cytologically detected in root meristematic nuclei. Activity was found over entire nuclei with no preferential nucleolar activity. -- An enzyme tentatively identified biochemically as poly(ADP-ribose) polymerase has been recorded for the first time from a higher plant tissue. Incorporation from nicotinamide adenine dinucleotide was demonstrated in cytologic sections of root meristematic cells. Incorporation was distributed over whole nuclei with no preferential nucleolar labeling. Intense activity was found in all tissues of ungerminated seed embryos.

Actions (login required)

View Item