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 Web of Science 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 Web of Science (22) Citing Articles via Google Scholar Google Scholar Articles by Huang, L. Articles by Castelfranco, P. A. Search for Related Content PubMed PubMed Citation Articles by Huang, L. Articles by Castelfranco, P. A. Agricola Articles by Huang, L. Articles by Castelfranco, P. A.

Metabolism and Enzymology

Regulation of 5-Aminolevulinic Acid Synthesis in Developing Chloroplasts ¹

I. Effect of Light/Dark Treatments in Vivo and in Organello

Department of Botany, University of California, Davis, California 95616

Intact chloroplasts isolated from greening cucumber (Cucumis sativus L. var Beit Alpha) cotyledons regenerated protochlorophyllide (Pchlide) in the dark with added cofactors from either exogenous glutamate or endogenous substrates. No other intermediates of the chlorophyll biosynthetic pathway accumulated. When inhibitors of 5-aminolevulinic acid (ALA) dehydratase were added, the Pchlide that failed to form was replaced by an excessive amount of ALA. When greening seedlings were returned to the dark, ALA-synthesizing activity in the isolated chloroplasts decreased dramatically and recovered if the dark-treated seedlings were again exposed to continuous white light prior to chloroplast isolation. Both the decline and the recovery of ALA-synthesizing activity were complete in approximately 50 minutes. Changes in chloroplast structure during in vivo light to dark and dark to light transitions (as evidenced by electron microscopy) were much slower. Exposing isolated chloroplasts from dark-treated seedlings to short white flashes before incubation transformed nearly all the endogenous Pchlide, but hardly stimulated ALA synthesis, suggesting that Pchlide does not act as a feed-back inhibitor on ALA synthesis. Chloroplasts isolated from dark-treated tissue did not form Pchlide from glutamate when incubated in the dark with added cofactors; moreover, the endogenous Pchlide did not turn over in organello. However, these chloroplasts did synthesize Pchlide from added ALA at the normal rate and synthesized ALA from glutamate at a reduced, but still significant, rate. Mg chelation was not affected by in vivo dark treatment.

This article has been cited by other articles:

				J. M. Frustaci, I. Sangwan, and M. R. O'Brian gsa1 Is a Universal Tetrapyrrole Synthesis Gene in Soybean and Is Regulated by a GAGA Element J. Biol. Chem., March 31, 1995; 270(13): 7387 - 7393. [Abstract] [Full Text] [PDF]