Lookup NU author(s): Dr Nawaporn Onkokesung
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2-C-Methyl-d-erythritol-2,4-cyclodiphosphate (MEcDP) is an intermediate of the plastid-localized 2-C-methyl-d-erythritol-4-phosphate (MEP) pathway which supplies isoprenoid precursors for photosynthetic pigments, redox co-factor side chains, plant volatiles, and phytohormones. The Arabidopsis hds-3 mutant, defective in the 1-hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate synthase step of the MEP pathway, accumulates its substrate MEcDP as well as the free tetraol 2-C-methyl-d-erythritol (ME) and glucosylated ME metabolites, a metabolic diversion also occurring in wild type plants. MEcDP dephosphorylation to the free tetraol precedes glucosylation, a process which likely takes place in the cytosol. Other MEP pathway intermediates were not affected in hds-3. Isotopic labeling, dark treatment, and inhibitor studies indicate that a second pool of MEcDP metabolically isolated from the main pathway is the source of a signal which activates salicylic acid induced defense responses before its conversion to hemiterpene glycosides. The hds-3 mutant also showed enhanced resistance to the phloem-feeding aphid Brevicoryne brassicae due to its constitutively activated defense response. However, this MEcDP-mediated defense response is developmentally dependent and is repressed in emerging seedlings. MEcDP and ME exogenously applied to adult leaves mimics many of the gene induction effects seen in the hds-3 mutant. In conclusion, we have identified a metabolic shunt from the central MEP pathway that diverts MEcDP to hemiterpene glycosides via ME, a process linked to balancing plant responses to biotic stress.
Author(s): Cabanelas DG, Wright LP, Paetz C, Onkokesung N, Gershenzon J, Concepción MR, Phillips MA
Publication type: Article
Publication status: Published
Journal: The Plant Journal
Print publication date: 01/04/2015
Online publication date: 24/03/2015
Acceptance date: 10/02/2015
ISSN (print): 0960-7412
ISSN (electronic): 1365-313X
Publisher: Wiley-Blackwell Publishing Ltd.
Notes: The communication between cytoplasm and nucleus is one of the mechanisms that plants use to fine-tune their responses to ever-changing environmental conditions. A concept of retrograde signalling has long been proposed as one of an early mechanism in plant responses to abiotic and biotic stress conditions. However, the identity and underline molecular mechanism of retrograde signalling molecules remain to be elucidated. Among different small signalling molecules, methyl erythriol cyclodiphosphate (MEcPP), an intermediate compound in MEP pathway, has been proposed to be a retrograde signalling molecule. This study shows that MEcPP signalling involves in plant resistance against specialist aphid, Brevicoryne brassicae, infestation
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