| | 1 | Author
| Peter Gölz, Jürgen Feierabend | Requires cookie* | | | Title
| Isoprenoid Biosynthesis and Stability in Developing Green and Achlorophyllous Leaves of Rye (Secale cereale L.)  | | | | Abstract
| Formation o f major prenylquinones and carotenoids was investigated by comparing the incorporation o f [14C]mevalonate into segments o f different age from green and etiolated leaves o f 22 °C-grown rye seedlings (Secale cereale L.) and from 32 °C-grown rye leaves which contained bleached and proplastid-like ribosome-deficient plastids, due to a heat-sensitivity o f 70S ribosome formation. The contents o f plastidic isoprenoids were much lower (between 2 -3 0 %) in the achlorophyllous than in green leaves. In green leaves [l4C]mevalonate incor poration into non-polar lipids and into plastoquinone was partially inhibited in the presence o f gabaculin, an inhibitor o f chlorophyll synthesis. However, except for ß-carotene, [,4C]mevalonate incorporation into isoprenoids continuously increased with age also in achlorophyllous etiolated or 32 °C-grown, as in green, leaves and was, except for ß-carotene and plastoquinone, higher in etiolated than in green leaves. In bleached 32 °C-grown leaves [l4C]mevalonate incorporation into all plastidic isoprenoids was strikingly (up to 45-fold) higher than in green control leaves. While degradation o f ß-carotene was greatly enhanced in bleached 32 °C-grown leaves, relative to green control leaves, and could thus compensate for a higher apparent synthesis, chase experiments did not reveal any marked differences o f the turnover o f other isoprenoids. The half times o f plastoquinone, phylloquinone and lutein were in the order o f 2 -3 days. W ithin a 24 h chase period a-tocopherol degradation did not become apparent. U ptake o f [14C]mevalonate and [l4C]isopentenyl pyrophosphate by isolated bleached plastids from 32 °C-grown leaves was much more rapid than by chloroplasts and resulted in higher precursor accumulation within the organelle. While mevalonate incorporation into iso prenoid lipids was not detected, isopentenyl pyrophosphate was incorporated into isoprenoid lipids, including plastoquinone. Rates o f incorporation by isolated chloroplasts or bleached plastids were o f similar order. The results illustrate that divergent types o f plastid differentia tion are associated with fundamental developmental changes o f the metabolic flow o f iso prenoid precursors between different products and compartments and, in particular, with changes o f import into the plastid compartment. | | | |
Reference
| Z. Naturforsch. 48c, 886—8 (1993); received May 14/September 27 1993 | | | |
Published
| 1993 | | | |
Keywords
| Carotenoids, Chlorophyll Form ation, Heat-Bleaching (o f Plastids), Isoprenoids, M evalonic Acid Incorporation | | | |
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| default:Reihe_C/48/ZNC-1993-48c-0886.pdf | | | | Identifier
| ZNC-1993-48c-0886 | | | | Volume
| 48 | |
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