During the present studies we attempted to answer the following questions: (i) Does low temperature alter the phosphorylation level of proteins in isolated nuclei? (ii) Does the nuclear phosphoprotein population change during a prolonged exposure of seedlings to cold? (iii) Do heat-stable proteins accumulate in the nucleus during a prolonged exposure of seedlings to cold? (iv) Are the answers to the above three questions related to freezing tolerance? A possible relationship between the observed cold-induced changes in phosphoproteins and the level of freezing tolerance was explored by comparing the results of experiments conducted on two cultivars (Apica and Trek) of alfalfa (Medicago sativa L.) which markedly differ in their capacity for cold acclimation. / We show that the phosphorylation level of several nuclear proteins is subject to rapid and reversible enhancement by low temperature. Several phosphoproteins were found to be constitutively present in the nucleus of both cultivars. The cold-induced stimulation of the phosphorylation of many of these proteins was much greater in the relatively freezing tolerant cultivar Apica than in the relatively freezing sensitive cultivar Trek. Population of nuclear phosphoproteins was found to be considerably more complex in Apica than in Trek. During a prolonged exposure of the seedlings to 4$ sp circ$C, additional phosphoproteins were imported into the nucleus of Apica seedlings but not those Trek. / Some heat-stable proteins were constitutively present in the nucleus of both cultivars. However during the 4-day cold treatment, a large accumulation of several additional heat-stable proteins was observed in the tolerant, but not the sensitive, cultivar. (Abstract shortened by UMI.)

Thesis (Ph. D.)--Rutgers University, 2007. / "Graduate Program in Microbiology and Molecular Genetics." Includes bibliographical references (p. 86-107).

Diss. (sammanfattning) Linköping : Univ., 2003. / Härtill 4 uppsatser.

Diss. (sammanfattning) Umeå : Univ., 2007. / Härtill 4 uppsatser.

Thesis (Ph.D.). / Written for the Division of Experimental Medicine, Dept. of Medicine. Title from title page of PDF (viewed 2008/03/12). Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--Rutgers University, 2008. / "Graduate Program in Cell and Developmental Biology." Includes bibliographical references (p. 102-115).

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 109-119).

Ph.D. (Biochemistry) / This study consistsof two parts namely: • Phosphoproteins in ripening mango fruit tissue: Effect of y-irradiation and various effectors on protein phosphorylation during the climacteric rise, climacteric peak and post-climacteric stages of ripening. • Protein kinase (EC 2.7.10 and EC 2.7.11) activities in ripening mango fruit tissue: Classification, purification and characterisation.

No description available.