This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Gee, R. Articles by Tolbert, N. E. Search for Related Content PubMed PubMed Citation Articles by Gee, R. Articles by Tolbert, N. E. Agricola Articles by Gee, R. Articles by Tolbert, N. E.

Metabolism and Enzymology

Changes in the Activity of the Chloroplastic and Cytosolic Forms of Dihydroxyacetone Phosphate Reductase during Maturation of Leaves ¹

Michigan State University, Department of Biochemistry East Lansing, Michigan 48824

Young or mature rosette leaves from spinach (Spinacia oleracea L.) plants growing in the field, in the greenhouse, or in a growth chamber under a regimen of 8 hours light and 16 hours dark contained 15 to 50 nanomoles per minute per gram wet weight of NADH:dihydroxyacetone phosphate reductase activity. Of this activity, 75 to 87% was the chloroplastic isoform and 25 to 13% was the cytosolic form. When plants were induced to senesce, as measured by stem elongation and flowering, the percentage of the two reductase isoforms in rosette or stem leaves changed to about 12% as the chloroplastic and 88% as the cytosolic isoform. The change in enzyme activity of the rosette leaves occurred within 3 days, before phenotypic changes were observed. Likewise, when plants senesced in continuous darkness, the percentage of chloroplastic to cytosolic reductase changed from 80:20% to 25:75% after 62 hours before changes in total protein or chlorophyll occurred. The ratio of activities did not change in the first 16 hours of darkness or overnight. In each case the change in ratio resulted from about a 75% decrease in activity of the chloroplastic isoform and up to 14-fold increase in cytosolic isoform. In spinach leaves purchased at a local market primarily only the cytosolic isoform remained. When plants were returned to normal day-nights, after 62 hours in continuous darkness, the activity of the chloroplastic isoform increased, but not to control levels after 3 days, while the cytosolic enzyme decreased within 1 day to normal day-night values. Changes in activity were not due to changes during in vitro assays in activation by thioredoxin for the chloroplastic isoform or fructose 2,6-phosphate for the cytosolic isoform.

This article has been cited by other articles:

				M. Miquel, C. Cassagne, and J. Browse A New Class of Arabidopsis Mutants with Reduced Hexadecatrienoic Acid Fatty Acid Levels Plant Physiology, July 1, 1998; 117(3): 923 - 930. [Abstract] [Full Text]