Johannes Zeidler

Cloning and heterologous expression of a cDNA encoding 1-deoxy-D-xylulose-5-phosphate reductoisomerase of Arabidopsis thaliana.

Various plant isoprenoids are synthesized via the non‐mevalonate pathway of isopentenyl diphosphate formation. In this pathway, 1‐deoxy‐D‐xylulose 5‐phosphate (DOXP), the first intermediate, is transformed to 2‐C‐methyl‐D‐erythritol 4‐phosphate (MEP) by an enzyme which was recently cloned from Escherichia coli. In order to find a plant homologue of this 1‐deoxy‐D‐xylulose 5‐phosphate reductoisomerase (DXR) we cloned a cDNA fragment from Arabidopsis thaliana which has high homology to the E. coli DXR. By expression of this fragment in E. coli we could demonstrate that it encodes a protein which transforms DOXP to MEP. The antibiotic fosmidomycin specifically inhibits this DXR enzyme activity.

Inhibition of the Non-Mevalonate 1-Deoxy-ᴅ-xylulose-5-phosphate Pathway of Plant Isoprenoid Biosynthesis by Fosmidomycin

Abstract Various bacterial and plastidic plant terpenoids are synthesized via the non-mevalonate1-deoxy-ᴅ-xylulose-5-phosphate (DOXP) pathway. The antibiotic and herbicidal compound fosmidomycin is known to inhibit growth of several bacteria and plants, but so far its mode of action was unknown. Here we present data which demonstrate that the DOXP pathway of isoprenoid biosynthesis is efficiently blocked by fosmidomycin. The results point to the DOXP reductoisom erase as the probable target enzyme of fosmidomycin.

Is Isoprene Emitted by Plants Synthesized via the Novel Isopentenyl Pyrophosphate Pathway

Abstract The incorporation of deuterium labeled 1-deoxy-ᴅ-xylulose into isoprene, emitted by three higher plants upon illumination, was analysed by headspace GC-MS. A high extent of incorporation into isoprene was found, indicating that isoprene is synthesized in higher plants via the novel isopentenyl pyrophosphate pathway, of which 1-deoxy-ᴅ-xylulose-5-phosphate is an intermediate. A new chemical synthesis of methyl [ 1-2H1]-1-deoxy-α/β-ᴅ-xyluloside from ᴅ-xylulose is presented.

The non-mevalonate isoprenoid biosynthesis of plants as a test system for new herbicides and drugs against pathogenic bacteria and the malaria parasite.

Higher plants and several photosynthetic algae contain the plastidic 1-deoxy-ᴅ-xylulose 5- phosphate / 2-C-methyl-ᴅ-erythritol 4-phosphate pathway (DOXP/MEP pathway) for isoprenoid biosynthesis. The first four enzymes and their genes are known of this novel pathway. All of the ca. 10 enzymes of this isoprenoid pathway are potential targets for new classes of herbicides. Since the DOXP/MEP pathway also occurs in several pathogenic bacteria, such as Mycobacterium tuberculosis, and in the malaria parasite Plasmodium falciparum, all inhibitors and potential herbicides of the DOXP/MEP pathway in plants are also potential drugs against pathogenic bacteria and the malaria parasite. Plants with their easily to handle DOXP/MEP-pathway are thus very suitable test-systems also for new drugs against pathogenic bacteria and the malaria parasite as no particular security measures are required. In fact, the antibiotic herbicide fosmidomycin specifically inhibited not only the DOXP reductoisomerase in plants, but also that in bacteria and in the parasite P. falciparum, and cures malaria-infected mice. This is the first successful application of a herbicide of the novel isoprenoid pathway as a possible drug against malaria.

Biosynthesis of 2-methyl-3-buten-2-ol emitted from needles of Pinus ponderosa via the non-mevalonate DOXP/MEP pathway of isoprenoid formation.

Abstract. The volatile hemiterpene 2-methyl-3-buten-2-ol (MBO) is emitted from the needles of several pine species from the Western United States and contributes to ozone formation in the atmosphere. It is synthesised enzymatically from dimethylallyl diphosphate (DMAPP). We show here that needles of Pinus ponderosa Laws. incorporated [1-2H1]-1-deoxy-D-xylulose (d-DOX) into the emitted MBO, but not D,L-[2-13C]mevalonic acid lactone. Furthermore, MBO emission was inhibited by fosmidomycin, a specific inhibitor of the second enzyme of the mevalonate-independent pathway of isopentenyl diphosphate and DMAPP formation, i.e. the 1-deoxy-D-xylulose 5-phosphate/2-C-methyl-D-erythritol 4-phosphate (DOXP/MEP) pathway. We thus prove that MBO emitted from needles of P. ponderosa is primarily formed via the DOXP/MEP pathway.

Isoprene and terpene biosynthesis

A major part of the volatile organic compounds (VOC) in the atmosphere originates from isoprenoids emitted from plants and in particular from trees (Sharkey et al. 1991; Helas et al. 1997; Kesselmeier and Staudt 1999). The largest proportions of the terpenoids emitted from vegetation consist of the hemiterpene isoprene, various monoterpenes and, much less important, certain sesquiterpenes. These days great importance is placed on monoterpene and isoprene emission due to their impact on atmospheric chemistry and ozone formation (Trainer et al. 1987; Lerdau et al. 1997). In order to obtain better estimates of biogenic terpene emissions, it is essential to understand the biochemical and physiological background involved in terpene biosynthesis and emission by plants.

Two Simple Methods for Measuring Isoprene Emission of Leaves by UV-Spectroscopy and GC-MS

Abstract Two new headspace methods for the analysis of isoprene emission from detached plant leaves are described. The first method is based on the UV-absorption of isoprene emitted by leaves inside quartz cuvettes and can be used for the quantitative spectrophotometric determination of isoprene production. The second technique is a micro-extraction method of isoprene from the cuvette air for GC analysis, and is very suitable for the determination of isotope-labeled isoprene by GC-MS.