Plant - Microbe Symbioses: the Good, the Bad and the Cheater! Jean-Michel Ané University of Wisconsin, Madison

Transcription

1 Plant - Microbe Symbioses: the Good, the Bad and the Cheater! Jean-Michel Ané University of Wisconsin, Madison

2 Symbiosis is a prolonged living together of different organisms that is beneficial for at least one of them. Anton de Bary (1879) CHEATER Species "A" BAD Parasitism Competition Competition Commensalism Neutralism Competition GOOD Mutualism Commensalism Parasitism Species "B" Continuum from mutualism to competition Variation of relationships over time and depending on: environmental conditions physiological conditions

3 Two major plant - microbe mutualisms ARBUSCULAR MYCORRHIZATION LEGUME NODULATION Primitive fungi: Glomeromycota More than 80% of higher plants Ancient symbiosis (460 MYA) No organogenesis Phosphate and nitrogen nutrition Protection against biotic and abiotic stresses Low level of host specificity Gram negative bacteria: rhizobia Restricted to legumes Recent symbiosis (60 MYA) Nodule organogenesis Nitrogen nutrition Generally highly specific

4 Molecular dialog in legume nodulation and arbuscular mycorrhization ARBUISCULAR MYCORRHIZAL FUNGI HOST LEGUME PLANT RHIZOBIA Strigolactones Flavonoids nodd structural nod genes Endo-mycorrhizeae Nodule organogenesis Myc factors Nod factors

5 Genetic analysis of symbiotic signaling Myc factors Myc receptors Nod factors Nod receptors (NFR1, NFR5) DMI1 DMI2 Arbuscular mycorrhization DMI3 IPD3 NSP1 NSP2 Legume nodulation Lateral root development 1. Common symbiotic signaling pathway 2. Control of plant development: Optimize TM LCO Promoter Technology, EMD Crop Biosciences

6 Origin of symbiotic associations Kistner and Parniske (2002) Existence of a master key for root symbioses Legume nodulation hijacked pre-existing mechanisms of arbuscular mycorrhization (AM)

7 An example of Cheater: non-fixing rhizobia Some rhizobia fix nitrogen more efficiently than others Nitrogen fixation requires a large amount of energy Rhizobia which are not fixing nitrogen efficiently are sanctioned The molecular mechanisms controlling this regulation are poorly understood Kiers et al. (2003)

8 The Bad from a plant perspective: Root - Knot Nematodes (RKN) Plant-parasitic nematodes Present in all ecological niches More than 2,000 plant species are susceptible Cause approximately 5% of global crop loss Galling of root system Lotus japonicus Tomato

9 Resistance of nfr1 and nfr5 mutants of Lotus japonicus to RKN infection Root knot nematodes (RKN) hijacked the Nod factor symbiotic signaling pathway Nem factor hypothesis Restricted to legumes? Weerasinghe et al. (2003)

10 The Bad from a human perspective: Salmonella and E. coli O157 Seed sprouts are reservoirs for Salmonella and E. coli which behave as root endophytes Taormina et al. (1999) Dong et al. (2003)

11 Medicago truncatula dmi1 mutants are over-infected by Salmonella DMI1 allows colonization of roots by symbiotic microbes but prevents infection by (pathogenic) saprophytes Other symbiotic genes play the same role? Plant genes controlling root colonization by enteric / endophytic bacteria? Dong et al. (2003)

12 Symbiotic mechanisms share common components: plant microbes animal microbes microbes microbes Symbiosis / Plant development crops yield (food and biofuel) Symbiosis / Defense reactions crops yield (food and biofuel) disease outbreaks

13 University of Wisconsin Madison, USA Muthusubramanian Venkateshwaran, Géraldine Lougnon, Désirée den Os, Arijit Mukherjee, Najia Zaman, Elsa Messinese, Li Huey Yeun, Dhileepkumar Jayaraman University of California Davis, USA Brendan K. Riely, Jeong-Hwan Mun, Douglas R. Cook Université Paul Sabatier Toulouse III, France Annick Barre, Pierre Rougé, Jean-Jacques Bono John Innes Centre, UK Anne Heckmann, Anne Edwards, Giles Oldroyd, Allan Downie University of York, UK Edgar Peiter, Dale Sanders Institut des Sciences du Végétal- CNRS Gif-sur-Yvette, France Zoltan Kevei, Peter Kalo, Adam Kondorosi, Eva Kondorosi University of Munich, Germany Myriam Charpentier, Martin Parniske Biological Research Center of Szeged, Hungary Attila Kereszt, György B. Kiss, Gabriella Endre NIAS, Japan Haruko Imaizumi-Anraku, Makoto Hayashi