Regulation of carotenoid biosynthesis in plants: evidence for a key role of hydroxymethylbutenyl diphosphate reductase in controlling the supply of plastidial isoprenoid precursors

Abstract

SummaryCarotenoids are isoprenoid pigments that function as photoprotectors, precursors of the hormone abscisic acid (ABA), colorants and nutraceuticals. A major problem for the metabolic engineering of high carotenoid levels in plants is the limited supply of their isoprenoid precursor geranylgeranyl diphosphate (GGPP), formed by condensation of isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) units usually synthesized by the methylerythritol phosphate (MEP) pathway in plastids. Our earlier work with three of the seven MEP pathway enzymes suggested that the first reaction of the pathway catalyzed by deoxyxylulose 5-phosphate synthase (DXS) is limiting for carotenoid biosynthesis during tomato (Lycopersicon esculentum) fruit ripening. Here we investigate the contribution of the enzyme hydroxymethylbutenyl diphoshate reductase (HDR), which simultaneously synthesizes IPP and DMAPP in the last step of the pathway. A strong upregulation of HDR gene expression was observed in correlation with carotenoid production during both tomato fruit ripening and Arabidopsis thaliana seedling deetiolation. Constitutive overexpression of the tomato cDNA encoding HDR in Arabidopsis did not increase carotenoid levels in etioplasts. By contrast, lightgrown transgenic plants showed higher carotenoid levels and an enhanced seed dormancy phenotype suggestive of increased ABA levels. The analysis of double transgenic Arabidopsis plants overproducing both the enzyme taxadiene synthase (which catalyzes the production of the non-native isoprenoid taxadiene from GGPP) and either HDR or DXS showed a twofold stronger effect of HDR in increasing taxadiene levels. Together, the data support a major role for HDR in controlling the production of MEP-derived precursors for plastid isoprenoid biosynthesis.

Effect of fosmidomycin on metabolic and transcript profiles of the methylerythritol phosphate pathway in Plasmodium falciparum

“…Fruit development in the tomato has been widely used as a system for these studies due to the observation that a significant increase in the supply of isoprenoid precursors is required to permit the massive accumulation of carotenoids that takes place during ripening. In this process, MEP-pathway key enzyme transcripts are accumulated; meanwhile, the transcript levels of the other MEP enzymes remain unchanged (Lois et al 2000, Rodriguez-Concepcion et al 2001, Botella-Pavia et al 2004. Despite the differences, P. falciparum intraerythrocytic development may be compared with tomato fruit ripening, since malaria parasites showed an increased biosynthesis of isoprenoids towards the end of schizogony (Fig.…”

“…Maximal transcript levels in the schizont stage were concomitant with an increase in the ubiquinone biosynthesis and a reduction of the respective MEP pathway intermediate. Several studies showed that in tomato fruit ripening the accumulation of carotenoids only requires increased levels of DXS, DXR, and LytB transcripts (Lois et al 2000, RodriguezConcepcion et al 2001, Botella-Pavia et al 2004). Interestingly, we observed a positive correlation in P. falciparum between enhanced isoprenoid biosynthesis (ubiquinones) and accumulation of transcripts encoding all enzymes of the MEP pathway except for DXS.…”

Induction of a leaf specific geranylgeranyl pyrophosphate synthase and emission of (E,E)-4,8,12-trimethyltrideca-1,3,7,11-tetraene in tomato are dependent on both jasmonic acid and salicylic acid signaling pathways

“…Thus we have identiWed two novel regulatory steps in the biosynthesis of TMTT in tomato. Kant et al (2004) have previously shown that DOXPS, the limiting step in plastidial IPP and DMAPP biosynthesis (Botella-Pavia et al 2004), was upregulated in tomato by spider mite-feeding ). This brings on the question why there are multiple steps in the biosynthesis of TMTT that are regulated.…”

Disruption of the 1-deoxy-D-xylulose-5-phosphate reductoisomerase (DXR) gene results in albino, dwarf and defects in trichome initiation and stomata closure in Arabidopsis

“…Exogenous application of GAs to the medium could partially rescue the dwarf phenotype of the pds3 mutant [30]. Other research indicated that levels of not only GAs but also other important compounds were decreased as a result of the metabolic disruption in the mutants of enzymes involved in the MEP pathway [21,[30][31][32][33][34]. However, no detailed analyses have been [30]).…”