This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
Synonyms: nerolidol biosynthesis, 4,8-dimethyl-1,3(E),7-nonatriene biosynthesis, DMNT biosynthesis
|Superclasses:||Biosynthesis → Secondary Metabolites Biosynthesis → Terpenoids Biosynthesis → Sesquiterpenoids Biosynthesis|
Some taxa known to possess this pathway include : Arabidopsis thaliana col, Cucumis sativus, Gossypium hirsutum, Malus domestica, Phaseolus lunatus, Populus tremula x Populus tremuloides, Populus trichocarpa x Populus deltoides, Vitis vinifera, Zea mays
Expected Taxonomic Range: Viridiplantae
The two acyclic homoterpenes (3E)-4,8-dimethylnona-1,3,7-triene (DMNT) and 4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT) are widespread constituents of flower fragrances [Boland89, Gabler91, Donath95]. These homoterpenes are released from the foliage of many plant species following herbivore damage [Boland92, Dicke94]. These compounds are part of the arsenal used in plant tritrophic 'indirect defense', which uses the volatile compounds to attract predators of the herbivores and help them locate their prey so that they do less damage to the host plants [Dicke99, Pare99, Turlings06]. It has been suggested that DMNT might be stored as a β-glucoside of its sesquiterpenoid precursor (3S,6E)-nerolidol and is cleaved by a β-glucosidase contained in the regurgitant of the feeding insect. DMNT would then be generated by an oxidative degradation as exemplified in this pathway. Synthesis of sesquiterpenes occurs in the cytosol, however, several studies have shown that the isoprene units of DMNT originate both from the cytosolic mevalonate pathway I and the plastidic methylerythritol phosphate pathway I [Hampel05, Bartram06].
About This Pathway
The FPP isoprenoid precursor to this pathway is first acted on by a terpene synthase to form nerolidol. Two different enantiomers may be formed. Different plant species have been observed to contain one or both of these enantiomers (see refs in [Donath95]) and plant enzymes that produce both the R-enantiomer [Schnee02] and the S-enantiomer [Degenhardt00, Bouwmeester99] have been experimentally identified.
The next step in the pathway is an oxidative degradation. This was long hypothesized to occur through the activity of a cytochrome p450 monooxygenase, but experimental proof was lacking until an Arabidopsis p450 enzyme, CYP82G1, was discovered that can catalyze the formation of DMNT from (3S,6E)-nerolidol when expressed in yeast [Lee10a]. CYP82G1 is unlikely to perform this function in planta because Arabidopsis thaliana col does not appear to have a nerolidol synthase. However, several potential orthologs of this enzyme in DMNT-producing species may be good candidates to test for DMNT synthase activty. For example, poplar produces DMNT [Arimura04] and has a member of the CYP82 family of enzymes, CYP82L2 with 53% amino acid identity to CYP82G1[Lee10a]. Although CYP82G1 acted on the (3S,6E)-nerolidol and a number of other plant species, such as Phaseolus lunatus (lima bean), exclusively act on the S-enantiomer, a broad survey of plants revealed that there are examples of species where both enantiomers can be used [Donath95]. And a direct test revealed that the R-enantiomer can be taken up and used by maize to produce DMNT [Schnee02].
Although there is now firm evidence that a cytochrome p450 enzyme can catalyze the formation of DMNT the exact mechanism of enzyme action is still being investigated. For instance, it is possible that CYP82G1 may promote the direct transformation of (3S,6E)-nerolidol to DMNT with the concomittant release of but-1-en-3-one as depicted in this pathway diagram. However, this reaction is labeled a "hypothetical" because this has not been experimentally verified. Interestingly, the formation of but-1-en-3-one has not been detected in reactions using an analogous compound TMTT when CYP82G1 is expressed in yeast (see TMTT biosynthesis) [Lee10a]. The authors state that but-1-en-3-one may not be detected because of its high chemical reactivity. However, it is also possible that a two-step conversion may occur that includes the formation of intermediate C-13 compound (E)-geranylacetone. This compound has been detected to exist in numerous plant species such as apple and Eucalyptus falcata [Piskorski10, Elaissi10]. Several researchers have examined this (3S,6E)-nerolidol to DMNT chemical conversion in different plants ( [Donath95] and see refs in [Lee10a]), but further work will be required to clarify the exact manner in which the final step of this pathway is executed.
Unification Links: PlantCyc:PWY-5434
Arimura04: Arimura G, Huber DP, Bohlmann J (2004). "Forest tent caterpillars (Malacosoma disstria) induce local and systemic diurnal emissions of terpenoid volatiles in hybrid poplar (Populus trichocarpa x deltoides): cDNA cloning, functional characterization, and patterns of gene expression of (-)-germacrene D synthase, PtdTPS1." Plant J 37(4);603-16. PMID: 14756770
Bartram06: Bartram S, Jux A, Gleixner G, Boland W (2006). "Dynamic pathway allocation in early terpenoid biosynthesis of stress-induced lima bean leaves." Phytochemistry 67(15);1661-72. PMID: 16580034
Bouwmeester99: Bouwmeester HJ, Verstappen FW, Posthumus MA, Dicke M (1999). "Spider mite-induced (3S)-(E)-nerolidol synthase activity in cucumber and lima bean. The first dedicated step in acyclic C11-homoterpene biosynthesis." Plant Physiol 121(1);173-80. PMID: 10482672
Degenhardt00: Degenhardt J, Gershenzon J (2000). "Demonstration and characterization of (E)-nerolidol synthase from maize: a herbivore-inducible terpene synthase participating in (3E)-4,8-dimethyl-1,3,7-nonatriene biosynthesis." Planta 210(5);815-22. PMID: 10805454
Dicke99: Dicke, M. (1999). "Evolution of induced indirect defense of plants." In: C.D. Harwell, R. Trollian, eds, The ecology and evolution of inducible defenses. Princeton University Press, Princeton, NJ, pp62-88.
Elaissi10: Elaissi A, Medini H, Larbi Khouja M, Simmonds M, Lynene F, Farhat F, Chemli R, Harzallah-Skhiri F (2010). "Variation in volatile leaf oils of eleven eucalyptus species harvested from korbous arboreta (Tunisia)." Chem Biodivers 7(7);1841-54. PMID: 20658674
Hampel05: Hampel D, Mosandl A, Wust M (2005). "Induction of de novo volatile terpene biosynthesis via cytosolic and plastidial pathways by methyl jasmonate in foliage of Vitis vinifera L." J Agric Food Chem 53(7);2652-7. PMID: 15796607
Lee10a: Lee S, Badieyan S, Bevan DR, Herde M, Gatz C, Tholl D (2010). "Herbivore-induced and floral homoterpene volatiles are biosynthesized by a single P450 enzyme (CYP82G1) in Arabidopsis." Proc Natl Acad Sci U S A. PMID: 21088219
Loughrin94: Loughrin JH, Manukian A, Heath RR, Turlings TC, Tumlinson JH (1994). "Diurnal cycle of emission of induced volatile terpenoids by herbivore-injured cotton plant." Proc Natl Acad Sci U S A 91(25);11836-40. PMID: 11607499
Schnee02: Schnee C, Kollner TG, Gershenzon J, Degenhardt J (2002). "The maize gene terpene synthase 1 encodes a sesquiterpene synthase catalyzing the formation of (E)-beta-farnesene, (E)-nerolidol, and (E,E)-farnesol after herbivore damage." Plant Physiol 130(4);2049-60. PMID: 12481088
Takabayashi94: Takabayashi, J., Dicke, M., Posthumus, M.A. (1994). "Volatile herbivore-induced terpenoids in plant-mite interactions: variation caused by biotic and abiotic factors." J. Chem. Ecol. 20:1329-1354.
Turlings06: Turlings TC, Ton J (2006). "Exploiting scents of distress: the prospect of manipulating herbivore-induced plant odours to enhance the control of agricultural pests." Curr Opin Plant Biol 9(4);421-7. PMID: 16723271
Li12: Li G, Kollner TG, Yin Y, Jiang Y, Chen H, Xu Y, Gershenzon J, Pichersky E, Chen F (2012). "Nonseed plant Selaginella moellendorfii has both seed plant and microbial types of terpene synthases." Proc Natl Acad Sci U S A 109(36);14711-5. PMID: 22908266
Van01a: Van Poecke RM, Posthumus MA, Dicke M (2001). "Herbivore-induced volatile production by Arabidopsis thaliana leads to attraction of the parasitoid Cotesia rubecula: chemical, behavioral, and gene-expression analysis." J Chem Ecol 27(10);1911-28. PMID: 11710601
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