Mathieu Gourgues
Associate Professor - University of Nice Sophia-Antipolis
Associate Professor - University of Nice Sophia-Antipolis
Email : mathieu.gourgues@sophia.inra.fr
Tel: +(33) 4 92 38 65 88
Fax: +(33) 4 92 38 65 87
Adress: Sophia Agrobiotech Institute
INRA/CNRS/University of Nice Sophia-Antipolis
400, route des Chappes,
BP 167
06903 Sophia Antipolis cedex
France
Tel: +(33) 4 92 38 65 88
Fax: +(33) 4 92 38 65 87
Adress: Sophia Agrobiotech Institute
INRA/CNRS/University of Nice Sophia-Antipolis
400, route des Chappes,
BP 167
06903 Sophia Antipolis cedex
France
Education
Since 2005: Associate Professor at Nice Sophia-Antipolis University
2003-2004: Post-Doc; Frederic Berger's group (ENS, Lyon, France).
Analysis of Arabidopsis thaliana mutants with altered fertilization.
2000-2003: PhD in phytopathology; Marc-Henri Lebrun's lab (Lyon, France).
of tetraspanin proteins in the penetration process of fungi.
1999: Master in Phytophathology (AgroParistech / University Paris XI).
1996: BSc in Biology (University of Pau, France).
2003-2004: Post-Doc; Frederic Berger's group (ENS, Lyon, France).
Analysis of Arabidopsis thaliana mutants with altered fertilization.
2000-2003: PhD in phytopathology; Marc-Henri Lebrun's lab (Lyon, France).
of tetraspanin proteins in the penetration process of fungi.
1999: Master in Phytophathology (AgroParistech / University Paris XI).
1996: BSc in Biology (University of Pau, France).
Research activity
Analysis of the molecular events involved in the establishment of a compatible interaction between Phytophthora parasitica and its hosts
Background
Oomycetes are responsible for economic losses over 3.5 billion euros per year in agriculture. Control methods are limited and based mainly on the use of fungicides or resistant varieties. Oomycetes were long considered as fungi but are more related to brown algae. Due to the specific physiology of these organisms, the search for new methods to fight against plant diseases caused by oomycetes must be done by a direct study of these organisms instead of transposing the results obtained for eumycetes. In this context, the identification of molecules capable of interfering with the establishment of the interaction with the host seems particularly relevant.
Studies analysing the early stages of the infection by oomycetes are particularly rare because of many technical limitations. Only a few publications report generation of ESTs, a proteomic analysis and transcriptomic analyzes two from penetration structures (appressoria) obtained on artificial surfaces or on plant. These studies suggest that a specific developmental program occurs during the early stages of infection.
In this context, developed a research project aiming at identifying Phytophthora parasitica genes whose expression is modulated during the establishment of a compatible interaction via a transcriptomic approach. The aim was in particular the identification of P. parasitica genes that are necessary for the differentiation and function of penetration structures (appressoria) but also those that encode proteins potentially exported to the host plant to modulate its defence responses.
Main results
- A DNA microarray containing the entire collection of ESTs was obtained for this project. The major advantage of this chip is the presence of 2000 united genes corresponding to genes expressed during the early stages of the interaction. They were obtained by using a simplified system of inoculation based on the use of onion skins which reproduces the initial stages of infection (differentiation penetration and penetration structures) (Kebdani and al, 2010). The array contains 4500 unique sequences.
- Search for P. parasitica penetration specific genes:
Transcriptomic analysis was developed to determine the modulation of gene expression during the first hours of the interaction (from differentiation of penetration structures to invasive growth). This study was performed using a pathosystem between the model plant Arabidopsis thaliana and P. parasitica that was developed by Agnès Attard (Attard et al, 2010; Jaouannet et al., 2012). Hybridization of cDNA on the chips were used to analyze five stages of the infection (2 stages corresponding to penetration of the host and 3 distinct stages of invasive growth) over a period of 30h after inoculation. The analysis of the gene expression profiles showed that a specific developmental program occurs during the P. parasitica penetration process. In particular, we have identified a subset of genes transiently accumulated in appressoria during penetration (Attard et al, 2014).
- Effectors are secreted during the penetration process:
Among the genes accumulated in appressoria, six encode proteins from the RXLR family of effectors. These proteins are known to be secreted by the oomycetes and imported into plant cells where they promote infection. We obtained a transcriptional fusion of the promoter of one of these genes with Green Fluorescent Protein (GFP) and showed that transcripts ecoding this effector is transiently accumulated during the penetration of the first plant cells (Attard et al, 2014).
Oomycetes are responsible for economic losses over 3.5 billion euros per year in agriculture. Control methods are limited and based mainly on the use of fungicides or resistant varieties. Oomycetes were long considered as fungi but are more related to brown algae. Due to the specific physiology of these organisms, the search for new methods to fight against plant diseases caused by oomycetes must be done by a direct study of these organisms instead of transposing the results obtained for eumycetes. In this context, the identification of molecules capable of interfering with the establishment of the interaction with the host seems particularly relevant.
Studies analysing the early stages of the infection by oomycetes are particularly rare because of many technical limitations. Only a few publications report generation of ESTs, a proteomic analysis and transcriptomic analyzes two from penetration structures (appressoria) obtained on artificial surfaces or on plant. These studies suggest that a specific developmental program occurs during the early stages of infection.
In this context, developed a research project aiming at identifying Phytophthora parasitica genes whose expression is modulated during the establishment of a compatible interaction via a transcriptomic approach. The aim was in particular the identification of P. parasitica genes that are necessary for the differentiation and function of penetration structures (appressoria) but also those that encode proteins potentially exported to the host plant to modulate its defence responses.
Main results
- A DNA microarray containing the entire collection of ESTs was obtained for this project. The major advantage of this chip is the presence of 2000 united genes corresponding to genes expressed during the early stages of the interaction. They were obtained by using a simplified system of inoculation based on the use of onion skins which reproduces the initial stages of infection (differentiation penetration and penetration structures) (Kebdani and al, 2010). The array contains 4500 unique sequences.
- Search for P. parasitica penetration specific genes:
Transcriptomic analysis was developed to determine the modulation of gene expression during the first hours of the interaction (from differentiation of penetration structures to invasive growth). This study was performed using a pathosystem between the model plant Arabidopsis thaliana and P. parasitica that was developed by Agnès Attard (Attard et al, 2010; Jaouannet et al., 2012). Hybridization of cDNA on the chips were used to analyze five stages of the infection (2 stages corresponding to penetration of the host and 3 distinct stages of invasive growth) over a period of 30h after inoculation. The analysis of the gene expression profiles showed that a specific developmental program occurs during the P. parasitica penetration process. In particular, we have identified a subset of genes transiently accumulated in appressoria during penetration (Attard et al, 2014).
- Effectors are secreted during the penetration process:
Among the genes accumulated in appressoria, six encode proteins from the RXLR family of effectors. These proteins are known to be secreted by the oomycetes and imported into plant cells where they promote infection. We obtained a transcriptional fusion of the promoter of one of these genes with Green Fluorescent Protein (GFP) and showed that transcripts ecoding this effector is transiently accumulated during the penetration of the first plant cells (Attard et al, 2014).
From Attard et al. BMC Genomics 2014, 15:538
- Penetration specific effectors contribute to pathogenicity:
We have shown that three RXLR proteins that are transiently accumulated during penetration of the host are able to interfere with plant defense responses. Indeed, they suppress the necrosis induced in response to different proteins from pathogens (one of the defense responses of plants corresponds to a programmed cell death of the infected cells that prevents colonization of surronding cells).
In addition, we showed that two of these proteins promote infection by Phytophthora parasitica when overexpressed in A. thaliana. We are currently trying to determine the molecular mechanisms that control this enhanced susceptibility. We have already shown that one of these proteins is capable of modulating the physiology of the plant hormone auxin and that this function contributes to the enhanced susceptibility of the transgenic lines (Evangelisti et al, 2013). We also showed that P. parasitica modulates the physiology of auxin as soon as it penetrates the first plant cell.
We have shown that three RXLR proteins that are transiently accumulated during penetration of the host are able to interfere with plant defense responses. Indeed, they suppress the necrosis induced in response to different proteins from pathogens (one of the defense responses of plants corresponds to a programmed cell death of the infected cells that prevents colonization of surronding cells).
In addition, we showed that two of these proteins promote infection by Phytophthora parasitica when overexpressed in A. thaliana. We are currently trying to determine the molecular mechanisms that control this enhanced susceptibility. We have already shown that one of these proteins is capable of modulating the physiology of the plant hormone auxin and that this function contributes to the enhanced susceptibility of the transgenic lines (Evangelisti et al, 2013). We also showed that P. parasitica modulates the physiology of auxin as soon as it penetrates the first plant cell.
From Evangelisti et al, 2013. New Phytologist : doi: 10.1111/nph.12270
Another from the penetration specific RXLR proteins is lethal when overexpressed in A. thaliana and its expression under the control of an inducible promoter causes a drastic stunting again suggesting a strong effect on plant development.
Taken together, these results suggest that proteins expressed by P. parasitica at the time of penetration are capable of modulating some essential functions of the host plant to allow infection. This work will be pursued by the search for the plant targets of these P. parasitica proteins.
These experiments should determine the molecular events that govern the function of these three effectors.
We have identified P. parasitica transcripts that are transiently accumulated during the early stages of infection. The evolution of this research project corresponds to the functional analysis of a series of candidate genes. Results obtained with RXLR effectors confirm that selection of candidate genes through a transcriptomic analysis is suitable for analysis of the early stages of infection. Our work should lead to a better understanding of the functioning of the P. parasitica appressorium and in particular to determine its role in the installation of the pathogen in its host plant in addition to its role in penetration.
Taken together, these results suggest that proteins expressed by P. parasitica at the time of penetration are capable of modulating some essential functions of the host plant to allow infection. This work will be pursued by the search for the plant targets of these P. parasitica proteins.
These experiments should determine the molecular events that govern the function of these three effectors.
We have identified P. parasitica transcripts that are transiently accumulated during the early stages of infection. The evolution of this research project corresponds to the functional analysis of a series of candidate genes. Results obtained with RXLR effectors confirm that selection of candidate genes through a transcriptomic analysis is suitable for analysis of the early stages of infection. Our work should lead to a better understanding of the functioning of the P. parasitica appressorium and in particular to determine its role in the installation of the pathogen in its host plant in addition to its role in penetration.