Transcriptional networks and regulators controlling defence-related programmed cell death
Plant resistance to disease involves costly defence responses, closely connected to plant physiological and developmental processes. A representative example is the hypersensitive response (HR), a localized form of programmed cell death (PCD) that prevents spreading of the pathogen beyond the inoculated zone. The sharp boundary of the HR suggests the existence of efficient mechanisms that control cell death and survival. Through the characterization of the transcription factor MYB30, a positive regulator of defence-related hypersensitive cell death, we have identified a subset of regulatory proteins that exert a spatio-temporal control in HR development in, and restriction to, the inoculated zone through distinct mechanisms. While continuing the characterization of this transcriptional complex, our work aims at providing a global view on the transcriptional changes and regulatory components controlling the triggering of the HR and its limitation to the infection site.
In addition, we have initiated the association of these molecular approaches with mathematical and statistical modelling methods. This integrative approach, developed in collaboration with colleagues at the Toulouse Mathematics Institute, aims at building a regulatory network that may be used to simulate reaction fluxes following reconstruction of the metabolic pathways involved. Our long term goal is to provide an integrated view of the regulatory network that shapes plant defence-related PCD.
The ubiquitin-proteasome system as a key regulator of plant immunity
In recent years, protein degradation mediated by the ubiquitin/proteasome system (UPS) has emerged as an essential regulator of plant immune responses. In line with this idea, we have identified MIEL1, a RING-type E3 ligase that interacts with MYB30 in the plant cell nucleus. This interaction leads to MYB30 ubiquitination and proteasomal degradation and thus to attenuation of plant defence responses. We currently pursue the functional characterization of MIEL1 and additional E3 ligase proteins during the regulation of plant defence responses.
In addition, in collaboration with Emmanuelle Graciet (Maynooth University, Ireland), we investigate novel roles of the N-end rule pathway, a subset of the ubiquitin-proteasome system that relates the in vivo half-life of a protein to the identity of its N-terminal amino acid residue, in modulating the timing and amplitude of the plant defence programme.
Protective roles of the Arabidopsis immune regulators during seed development
Despite extensive genetic screening and genome-wide expression profiling studies, little is known about the molecular components that mediate integration of defence signalling and developmental pathways in plants. Transcription factors are considered as “cellular hubs”, acting as integration centres at which different signalling pathways converge, as they are able to adapt the transcriptional reprogramming triggered during plant responses to environmental stimuli. Along these lines, our recent data suggests that, beyond the well characterized role of MYB30 and co-regulatory proteins during plant immune responses, these transcriptional regulators may play important developmental functions during early embryogenesis. Moreover, additional results support the idea that these developmental roles may be linked to protective roles against pathogen transmission from seed-bearing plant to seed and, likely, from seed to seedling. Our work aims at providing a connection between plant developmental processes, pathogen propagation through seeds and vertical transmission of pathogens.
Emmanuelle Graciet (Maynooth University, Ireland)
Gwyneth Ingram (RDP, Lyon)
Bertrand Dubreucq (IJPB, Versailles)
Frédéric Domergue, Jérôme Joubès, Sébastien Mongrand (LBM, Bordeaux)
Núria Sanchez-Coll (CRAG, Barcelona, Spain)
David Honys (Institute of Experimental Botany, Prague, Czech Republic)
Alain Jauneau, Cécile Pouzet (Imaging Facility FR AIB, Toulouse)
David Rengel (LIPM)
Philippe Besse, Sébastien Déjean (IMT, Toulouse)
- INRA BAP Department PhD fellowship (2016-2019). “Deciphering the protective roles of transcriptional regulators of disease resistance during seed development in Arabidopsis thaliana”. Coordinator: S. Rivas; 47 k€
- Région Midi-Pyrénées PhD Fellowship (2016-2019). “Deciphering the protective roles of transcriptional regulators of disease resistance during seed development in Arabidopsis thaliana”. Coordinator: S. Rivas; 65 k€.
- INRA BAP Division Scientific Project (2016-2017). “ Laser Microdissection for Comparative Seed Compartment Data”, Coordinator: G. Ingram (RDP), partners: B. Dubreucq, S. Rivas; 25 k€.
- INRA SPE Division PhD fellowship (2013-2016). “Towards systemic modelling of the MYB transcriptional rheostat that regulates defence responses in Arabidopsis thaliana”, Coordinator: S. Rivas; 47 k€
- Région Midi-Pyrénées PhD Fellowship (2013-2016). “Towards systemic modelling of the MYB transcriptional rheostat that regulates defence responses in Arabidopsis thaliana”, Coordinator: S. Rivas; 60 k€
- INRA SPE Department Scientific Project (2014-2015). “New roles for innate immunity during seed development in Arabidopsis thaliana”. Coordinator: S. Rivas; 30 k€.
- FR AIB Research Grant (2014). “Towards translational research: study of the role of Arabidopsis MYB30 in the establishments of tomato defence responses”. Coordinators: S. Rivas/C.Audran; 10 k€.
- CNRS PEPS BMI (Biology, Mathematics and Informatics) Interdisciplinary project (2013-2014). “Systemic modelling of transcriptional networks regulating Arabidopsis defence”. Coordinator: S. Rivas; 20 k€
- ANR Young Investigator Grant (2009 - 2012). “AtMYB30 SUMOylation, phosphorylation and ubiquitination studies”. Coordinator: S. Rivas; 215 k€