Inhibition of carotenoid biosynthesis

BIRD C R, RAY J A, FLETCHER J D, BONIWELL J M, BIRD A S, TEULIERES C, BLAIN I, BRAMLEY P M and SCHUCH w (1991) Using antisense RNA to study gene function inhibition of carotenoid biosynthesis in transgenic tomatoes , BioTechnology, 9, 635-9. 

BOUVIER F, d harlingue A, BACKHAUs R A, KUMAGAi H and CAMARA B (2000) Identification of neoxanthin synthase as a carotenoid cyclase pmalog , FEBSLetters, 267, 6346-52. BRAMLEY P M (1993) Inhibition of carotenoid biosynthesis , in Yoimg A J and Britton G, Carotenoids in Photosynthesis, London, Chapman and HaU, 127-59. 

The inhibition of carotenoid biosynthesis removes these protective pigments from the chloroplasts and leads to damaging effects within them. Herbicides that have been shown to interfere with carotenoid... 

F, Bleaching inhibition of carotenoid biosynthesis at the phytoene desaturase step (PDS) Pyridazinones Nicotinanilides Others 12... 

Because bleaching can also be caused by inhibition of carotenoid biosynthesis, we tested our compounds for effects on carotenoid content. There was a dose-dependent increase in carotenoid content using the series 1 emodin analogues (Fig. 1.8). This was seen in both monocots and dicots and was not observed with the series 2 analogues. 

KUMAGAI, M. H., DONSON, J., DELLA-CIOPPA, G., HARVEY, D., HANLEY, K., GRILL, L. K., Cytoplasmic inhibition of carotenoid biosynthesis with virus-derived RNA, Proc. Natl. Acad. Sci. USA 1995, 92,1679-83. 

Table 4.1.1 presents IC50S of commercial herbicides for inhibition of carotenoid biosynthesis obtained in vivo according to Ref [26). The assay is easier to run than the early radioactive approach with unicellular cyanobacteria [35], giving in three cases differing results. This may be caused by differences in target site sensitivity, uptake and translocation effects or metabolism of the herbicides in the treated bacteria cells of the early test assays. Table 4.1.1 also presents physical and acute oral toxicity data [36, 37). 

Removal of a p-nitro group from peroxidative diphenyl ethers drastically reduced their peroxidative activity while increasing the inhibition of carotenoid biosynthesis, provided a substituted formamide substituent is present in the metaposition (1, Fig. 4.1.3). Both the o- and p-derivatives are inactive (reviewed in Ref [27]). Lipophilicity of the phenoxy ring and chain length of the alkyl group up to five carbon atoms increases activity, while branching results in a loss of activity. QSAR equations of the effect of the carbonamide substituent have been calculated [38]. No commercial product has been developed. 

INHIBITION OF CAROTENOID BIOSYNTHESIS AND LHC II ASSEMBLY IN METHYL PARATHION TREATED WHEAT SEEDLINGS ... 

Inhibition of Carotenoid Biosynthesis and LHC II Assembly in Methyl Parathion Treated... 

C3a4b. Inhibition of 4-hydroxyphenyl-pyruvate-dioxygenase (F2) C3a4c. Inhibition of carotenoid biosynthesis (unknown target) (F3)... 

Energy transfer between chlorophyll and carotenoids occurs by two pathways a static route involving no intramolecular motion, and a dynamic mechanism which involves movement of the two chromophores. Sufficient carotenoid molecules are normally present to deexcite the chl and O2 present, but if this concentration is reduced, for example, by inhibition of carotenoid biosynthesis, then 2 accumulates, and rapid destruction of membranes occurs by peroxidation. " ... 

Figure 5.10 represents an outline of the isoprenoid pathway in plants and highlights the importance of this pathway in providing molecules essential for the metabolism of plant cells. Many of the isoprenoids (terpenoids) derived from the pathway are unique to plants, and therefore their biosynthesis would be a good herbicide target. Indeed, this has already been seen in Chapter 4 with the inhibition of carotenoid biosynthesis from phytoene by several classes of successful herbicides. In this section, the evidence for herbicide inhibition of other sites within the isoprenoid pathway is reviewed. 

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