JASMONATE SIGNALING · Analysis of the ORA47 transcription factor involved in jasmonic acid signal transduction in Arabidopsis thaliana
FP6 — Marie Curie Actions (Human Resources and Mobility)
- Duration
- 2006-09-01 → 2008-08-31
- EU contribution
- €156,625
- Participants
- 1
- Scheme
- EIF
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Results in brief
Final Activity Report Summary - JASMONATE SIGNALING (Analysis of the ORA47 transcription factor involved in jasmonic acid signal transduction in Arabidopsis thaliana)
Jasmonic acid (JA) and derivatives are plant defence hormones involved in biotic or abiotic stress responses in plants. Stress induces JA biosynthesis via the so-called octadecanoid pathway. All JA biosynthesis genes are induced by JA indicating that JA initiates an auto-stimulatory loop. In the host lab the AP2-domain transcription factor ORA47 from Arabidopsis thaliana has been identified as a regulator of the JA-responsive expression of several JA biosynthesis genes, including the AOC2 gene. The expression of ORA47 gene itself is transiently induced by JA. It has been shown that the protein synthesis inhibitor cycloheximide did not inhibit JA-responsive expression of the AOC2 gene, indicating that de novo synthesis of ORA47 protein is not necessary. The working hypothesis is that JA does not induce JA biosynthesis gene expression by increasing ORA47 protein abundance, but activates pre-existing ORA47 protein. The main aim of the project was thus to identify proteins that could interact with and / or activate ORA47 in the context of JA signalling. Two approaches were used to identify ORA47 interactors, the TAP-tag method and the yeast-two hybrid screening technique. The first approach was to express ORA47 tagged with a TAP-tag in Arabidopsis plants. Despite a correct expression of the tagged ORA47, the TAP tag used did not allow efficient recovery of the tagged protein. Thus this technique was unsuccessful. However, using yeast-two hybrid screening, two potential ORA47 interactors were identified. Interaction was confirmed using an in vitro interaction assay. Relevance and function of these interactions in vivo are still under investigation. Recently a new family of proteins called JAZ were discovered which regulate JA-responsive expression of certain genes. These proteins regulate the JA-responsive activity of the transcription factor AtMYC2 at the protein level. Interaction of ORA47 with JAZ proteins was tested using yeast two-hybrid assays. None of the 12 JAZ protein family members interacted with ORA47 in this assay. During this project, two new interactors of ORA47 were identified, whereas JAZ proteins, newly identified key regulators of a certain branch of the JA response pathway, are not interacting with ORA47. Further experimentation is needed to elucidate the involvement of these new interactors in regulation of ORA47 activity.
Data: CORDIS, © European Union
Project objective
Plants defend themselves against stress, including pathogen or herbivore attack, via biosynthesis of protective secondary metabolites and defence proteins. Stress induces this response via a complex signal transduction network with jasmonic acid (JA) and r elated compounds as major players.Stress induces JA biosynthesis via the so-called octadecanoid pathway. The genes encoding octadecanoid pathway enzymes are themselves induced by JA, indicating that JA initiates an autostimulatory loop. It is unknown how stress activates the octadecanoid pathway, how the produced JA is perceived, and how that leads to expression of JA biosynthesis genes and defence genes.Knowledge about these processes will contribute to enhanced productivity of industrially and agronomic ally important plant species. The host group has identified the AP2-domain transcription factor ORA47, which regulates the JA-responsive expression of JA biosynthesis genes in Arabidopsis thaliana.The protein synthesis inhibitor cycloheximide does not inhibit JA-induced JA biosynthesis gene expression, indicating that de novo synthesis of ORA47 protein is not necessary.Therefore, JA activates pre-existing ORA47 protein, for example via a change in the posttranslational modification (e.g. phosphorylation) status, and/or via changes in the interaction with accessory regulatory proteins. ORA47 is the first terminal component of the JA signal transduction pathway characterized in Arabidopsis.The main aim of this research proposal is to identify key proteins t hat interact with and/or activate ORA47 in a JA-responsive manner. Another aim is to study whether ORA47 is posttranslationally modified, and if so, whether JA affects the modification status.One experimental approach uses a modified yeast two-hybrid system called Cytotrap system. Another approach uses transgenic Arabidopsis plants expressing TAP-tagged ORA47 protein, to isolate proteins interacting with ORA47 via tag-guided co-purification.
Original text from CORDIS.
Participants
- LEIDEN UNIVERSITY · LEIDENCoordinatorNetherlands
Links
Data: CORDIS, © European Union