Decreased and increased expression of the subunit CHL I diminishes Mg chelatase activity and reduces chlorophyll synthesis in transgenic tobacco plants
- authored by
- Jutta Papenbrock, Erhard Pfündel, Hans Peter Mock, Bernhard Grimm
- Abstract
The chelation of Fe2+ and Mg2+ ions forms protoheme IX and Mg-protoporphyrin IX, respectively, and the latter is an intermediate in chlorophyll synthesis. Active magnesium protoporphyrin IX chelatase (Mg-chelatase) is an enzyme complex consisting of three different subunits. To investigate the function of the CHL I subunit of Mg-chelatase and the effects of modified Mg-chelatase activity on the tetrapyrrole biosynthetic pathway, we characterized N. tabacum transformants carrying gene constructs with the Chl I cDNA sequence in antisense and sense orientation under the control of the CaMV 35S promoter. Both elevated and diminished levels of Chl I mRNA and Chl I protein led to reduced Mg-chelatase activities, reflecting a perturbation of the assembly of the enzyme complex. The transformed plants did not accumulate the substrate of Mg-chelatase, protoporphyrin IX, but the leaves contained less chlorophyll and possessed increased chlorophyll(a/b) ratios, as well as a deficiency of light-harvesting chlorophyll binding proteins of photosystems I and II. The expression and activity of several tetrapyrrolic enzymes were reduced in parallel to lower the Mg-chelatase activity. Consistent with the lower chlorophyll contents, the rate-limiting synthesis of 5-aminolevulinate was also decreased in the transgenic lines analyzed. The consequence of reduced Mg-chelatase on early and late steps of chlorophyll synthesis, and on the organization of light harvesting complexes is discussed.
- Organisation(s)
-
Institute of Botany
Institute of Plant Genetics
- External Organisation(s)
-
Leibniz Institute of Plant Genetics and Crop Plant Research (IPK)
Julius Maximilian University of Würzburg
- Type
- Article
- Journal
- Plant Journal
- Volume
- 22
- Pages
- 155-164
- No. of pages
- 10
- ISSN
- 0960-7412
- Publication date
- 01.04.2000
- Publication status
- Published
- Peer reviewed
- Yes
- ASJC Scopus subject areas
- Genetics, Plant Science, Cell Biology
- Electronic version(s)
-
https://doi.org/10.1046/j.1365-313X.2000.00724.x (Access:
Unknown)
