< Back to previous page

Publication

Dynamic protein complexes involved in plant secondary metabolism

Book - Dissertation

In plants, the existence of protein complexes has been well documented for primary metabolic pathways. However, little evidence supporting the formation of multienzyme complexes or so-called metabolons in plant secondary metabolism is available. Also many of the regulatory mechanisms that steer the production of secondary metabolites still need to be fully elucidated. Here, we used a proteomics approach (Blue Native/SDS-PAGE and tandem affinity purification combined with mass spectrometry (TAP-MS)) to investigate the occurrence, composition and dynamics of protein complexes and to identify new players in both metabolic and regulatory pathways involved in plant secondary metabolism. For the monolignol biosynthesis pathway in Arabidopsis, the cytosolic enzymes PAL1, PAL2 and CAD4 appeared to form multimeric complexes, while the CYP450 enzymes C4H and C3H1 seemed to be involved in a large, ER-associated protein complex. Moreover, an esterase/lipase/thioesterase (ELT) of unknown function and a CYP450 enzyme involved in phytoalexin biosynthesis, were shown to copurify both with C4H and C3H1. TAP-MS analysis of a set of key players of the jasmonate (JA) signalling cascade showed that this pathway involved the formation of dynamic protein complexes of which the composition changed upon treatment with JA. Furthermore, a number of new players involved in JA signalling was discovered. JAZ1 was shown to interact with a previously uncharacterized protein NOVEL INTERACTOR OF JAZ (NINJA), which in its turn recruited the co-repressor TOPLESS to the JA signalling module. We could further demonstrate that the RING E3 ligase KEEP ON GOING (KEG), involved in abscissic acid (ABA) signalling, interacts with the Jas domain of a subset of JAZ proteins. Moreover, mutant analysis suggested a role for KEG as a negative regulator in JA signalling. These findings underscore the relevance of protein complexes both in the regulatory- and the biosynthetical pathways of plant secondary metabolism. Insight in the composition and formation of these complexes could be valuable for the development of biotechnological applications that boost or alter the production of secondary metabolites.
Publication year:2010
Accessibility:Closed