ERC FUNDED PROJECTS

This project focuses on two questions about host/parasite interactions: how do biotrophic plant pathogens suppress host defence? and, what is the basis for pathogen specialization on specific host species? A broadly accepted model explains resistance and susceptibility to plant pathogens. First, pathogens make conserved molecules ( PAMPS ) such as flagellin, that plants detect via cell surface receptors, leading to PAMP-Triggered Immunity (PTI). Second, pathogens make effectors that suppress PTI. Third, plants carry 100s of Resistance (R) genes that detect an effector, and activate Effector-Triggered Immunity (ETI). One effector is sufficient to trigger resistance. Albugo candida (Ac) (white rust) strongly suppresses host defence; Ac-infected Arabidopsis are susceptible to pathogen races to which they are otherwise resistant. Ac is an oomycete, not a fungus. Arabidopsis is resistant to races of Ac that infect brassicas. The proposed project involves three programs. First ( genomics, transcriptomics and bioinformatics ), we will use next-generation sequencing (NGS) methods (Solexa and GS-Flex), and novel transcriptomics methods to define the genome sequence and effector set of three Ac strains, as well as carrying out >40- deep resequencing of 7 additional Ac strains. Second, ( effectoromics ), we will carry out functional assays using Effector Detector Vectors (Sohn Plant Cell 19:4077 [2007]), with the set of Ac effectors, screening for enhanced virulence, for suppression of defence, for effectors that are recognized by R genes in disease resistant Arabidopsis and for host effector targets. Third, ( resistance diversity ), we will characterize Arabidopsis germplasm for R genes to Ac, both for recognition of Arabidopsis strains of Ac, and for recognition in Arabidopsis of effectors from Ac strains that infect brassica. This proposal focuses on Ac, but will establish methods that could discover new R genes in non-hosts against many plant diseases.

2 498 923 €

Start date: 2009-01-01, End date: 2014-06-30

The gut is the major interface between microbes and their animal hosts and constitutes the main entry route for pathogens. As a consequence gut cells must be armed with efficient immune defenses to combat invasion and colonisation by pathogens. However, the gut also harbors a flora of commensal bacteria, with potentially beneficial effects for the host, which must be tolerated without a chronic, and harmful, immune response. In recent years Drosophila has emerged as a powerful model to dissect host-pathogen interactions, leading to the paradigm of antimicrobial peptide regulation by the Toll and Imd signaling pathways. The strength of this model derives from the availability of powerful and cost effective genetic and genomic tools as well as the high degree of similarities to vertebrate innate immunity. However, in spite of growing interest in gut mucosal immunity generally, very little is known about the immune response of the Drosophila gut. Using powerful new tools and those developed in the study of the systemic response, we propose to raise our understanding of Drosophila gut immunity to the same level as that of systemic immunity within the next five years. This project will involve integrated approaches to dissect not only the gut immune response but also gut homeostasis in the presence of commensal microbiota, as well as strategies used by entomopathogens to circumvent these defenses. We believe that the fundamental knowledge generated on Drosophila gut immunity will serve as a paradigm of epithelial immune reactivity and have a wider impact on our comprehension of animal defense mechanisms.

1 485 627 €

Start date: 2009-04-01, End date: 2014-03-31

The molecular cross talks occuring at the interface between the intestinal epithelium and bacterial flora will be studied at two levels : (i) how commensals and pathogens affect innate immune signalling, thereby leading to tolerance of the resident microbiota, and inflammatory rejection of the pathogens. The theme of commensals and pathogens regulating this innate response, particularly how they respectively strengthen or weaken the network of humoral and cellular epithelial defense systems will be central here. (ii) How, in molecular and cellular terms, bacteria affect epithelial renewal. The gut of a germ-free mouse and of a conventional mouse show dramatic differences marked by global immaturity and slow epithelial renewal in absence of flora. In front of pathogens, the actual role plaid in the disease in altering the kinetics of epthelial repair is unknown. The aim of this project is to study how commensals and pathogens affect intestinal epithelial renewal, particularly the key steps of the whole developmental process such as lineages decisions, entry in cycle and proliferation, migration and final differentiation, decision to engage in cell death. In order to address these fundamental questions, we will study a commensal microorganism : Lactobacillus casei, and a pathogenic microorganism : Shigella flexneri as model organism, and will develop several novel systems such as reverse genetics of Lactobacilli, development of intestinal crypt models in vitro to study bacterial interactions, and development of a mouse model showing susceptibility to human-specific enteroinvasive pathogens. This project aims at interfacing microbiology, cell biology, and development biology around the concept of microbes manipulating intestinal epithelial homeostaesis. It also includes a strong component of therapeutic development aimed at identifying novel anti-infectious strategies and options to speed up epithelial restitution upon infectious-inflammatory damages.

2 356 350 €

Start date: 2009-02-01, End date: 2014-03-31

Mast cells (MC) are best known for their central role in allergic disease but, more recently, MC have also been considered as important elements of the immune system in general. Since the original recognition, more than 10 years ago, that MC may have immunological functions beyond allergic disease, a very long list of physiological and pathological conditions has been accumulated in which MC have been suggested to play important roles. However, definitive evidence for MC functions in areas as important as innate and adaptive immunity, autoimmunity, transplant rejection, vascular diseases, tumour growth, and wound healing are currently mostly lacking. A major hurdle in this field is the lack of a genetically-defined mouse mutant selectively deficient in all MC. The available MC-deficiency models are based on mutations in the pleiotropic growth factor receptor Kit. Kit mutations cause many defects in multiple lineages inside and outside of the immune system, are mostly unavailable on pure genetic backgrounds, and are difficult to combine with other gain or loss of function mutations. We have now generated a new mouse strain that is selective MC-deficient. Cre recombinase (Cre)-mediated MC eradication takes advantage of the genotoxic property of Cre, and does not require Cre-mediated deletion of loxP-flanked genes in MC. These MC-deficient mice are now available for the proposed project on pure C57BL/6 and BALB/c mouse backgrounds. For proof of principle, we are not only demonstrating that MC are absent from these mutants but also provide evidence that these MC-deficient inbred mice behave very differently compared to MC-deficient, Kit-deficient mice in classical assays previously used to suggest in vivo MC functions. Based on these findings, and given the need for conclusive in vivo studies to advance this area of immunology, I propose to develop and lead a research program addressing the in vivo functions of MC in key areas of immunology.

1 880 000 €

Start date: 2009-12-01, End date: 2015-11-30