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Research » Department of Genetic Engineering » Professors/Researchers » Dr. Heil Martin » Plant Ecology Laboratory

Laboratory of Plant Ecology: Induced and indirect plant resistance traits

Plants are constantly attacked by herbivores and pathogens. Because they cannot escape from undesirable conditions, plants have evolved phenotypic plasticity to adjust their phenotype to the current needs [1]. In our group (photo del grupo) we are interested in strategies that plants use for their defence. We study direct defences, which are usually mediated by toxins, and indirect defences via plant-carnivore mutualisms [2]. Obligate ant-plant mutualisms in particular can be highly sophisticated, allow the plant to get rid of almost all types of natural enemies, and include specific adaptations that make the mutualism specific and successful [3-5]. Plants even make use of volatile cues that are emitted from infected or infested neighbours. Responding adequately to the smell of suffering neighbours benefits plant survival in the natural environment [6].

 

We are ecologists and study various systems and mechanism as a broad approach to plant defence strategies. We work with beans with the aim to understand their inducible resistance to pathogens and herbivores, and we study an ant-Acacia mutualism to understand which adaptations are required to maintain this type of highly sophisticated defence-for-housing mutualism.


Wildtypes and cultivars of beans (Phaseolus lunatus and Phaseolus vulgaris) are screened for genotypes that resist infection or in which resistance can easily be induced (Elizabeth) via odour-mediated signalling processes (“plant communication”) (Saraí). Volatiles that are emitted from damaged or infected plants induce resistance in neighbouring plants [1-3], mediate systemic resistance in response to local damage [2, 4] and attract parasitoids and other carnivores that mediate an indirect defence of the plant [5]. Most of these effects are induced in response to a fist damaging event. Plants do not feel pain but still respond to damage with hundreds of induced defensive responses, including volatile emission, the secretion of extrafloral nectar and numerous direct defences. How can plants perceive that they are damaged? Currently, we are searching for the compounds that mediate this “damaged-self recognition” [6] (Ariana).


 Volatiles can, however, also be used by herbivores as host-localisation cues and it appears possible that even pathogens manipulate the odour of their  host plant in order to facilitate the attraction of their vectors (Ithaí). Due to the numerous disadvantages of facultative mutualisms it appears more reliable to engage obligate mutualists in defensive interactions, which do not need to be attracted by signals that can also be used by non-mutualistic organisms. This type of mutualism exists for example in the case of Central American Acacia plants, which are inhabited by defending ants of the genus Pseudomyrmex. The plants provide food rewards and nesting space [7, 8] to ant colonies that nest on these plants. In order to keep the mutualism stable, both partners must be phenotypically plastic and specialized to make efficient use of the rewards and services that are provided by the other partner [8-10]. For example, the extrafloral nectar plants produce to nourish their ant inhabitants is right in sugars and amino acids but at the same time protected from infection by means of specific antimicrobial proteins [11-13]. We study the chemical composition of food bodies (Domancar), because they need to be defended from non-mutualists and at the same time represent a palatable food source for the mutualistic ants. We also investigate how ant queens (Rosario) can localise their specific host plants and how food reward production can be adjusted to the species of ant that inhabits an Acacia shrub (Daniel). Our central aim is to understand how plants employ the phenotypic plasticity of their resistance traits to defend themselves against their enemies. We hope that some of these traits in the future can be used as environmentally friendly crop protection strategies.  

 

Bibliography

  1. Heil, M. (2010) Plastic defence expression in plants. Evol. Ecol. 24, 555-569
  2. Heil, M. (2008) Indirect defence via tritrophic interactions. New Phytol. 178, 41-61
  3. Heil, M., et al. (2009) Divergent investment strategies of Acacia myrmecophytes and the coexistence of mutualists and exploiters. Proc. Natl. Acad. Sci. USA 106, 18091–18096
  4. Heil, M., et al. (2004) Evolutionary change from induced to constitutive expression of an indirect plant resistance. Nature 430, 205-208
  5. Heil, M., et al. (2005) Post-secretory hydrolysis of nectar sucrose and specialization in ant/plant mutualism. Science 308, 560-563
  6. Heil, M., and Silva Bueno, J.C. (2007) Within-plant signaling by volatiles leads to induction and priming of an indirect plant defense in nature. Proc. Natl. Acad. Sci. USA 104, 5467-5472
  7. Heil, M., and Ton, J. (2008) Long-distance signalling in plant defence. Trends Plant Sci. 13, 264-272
  8. Heil, M., and Karban, R. (2010) Explaining evolution of plant communication by airborne signals. Trends Ecol. Evol. 25, 137-144
  9. Yi, H.-S., et al. (2009) Airborne induction and priming of plant resistance to a bacterial pathogen. Plant Physiol. 151, 2152–2161
  10. Heil, M., et al. (2010) Chemical communication and coevolution in an ant-plant mutualism. Chemoecology 20, 63-
  11. González-Teuber, M., et al. (2009) Pathogenesis-related proteins protect extrafloral nectar from microbial infestation. Plant J. 58, 464–473
  12. González-Teuber, M., and Heil, M. (2009) Nectar chemistry is tailored for both attraction of mutualists and protection from exploiters. Plant Signal. Behav. 4, 809-813
  13. González-Teuber, M., et al. (2010) Glucanases and chitinases as causal agents in the protection of Acacia extrafloral nectar from infestation by phytopathogens. Plant Physiol. 152, 1705–1715