Deciphering the role of volatile compounds in the resistance induction in common bean (Phaseolus vulgaris): from genomics to the field.

Project leaders

Michelina Ruocco, Martin Heil

Agreement

MESSICO - CONACYT-expired - Consejo Nacional de Ciencia y Tecnologia

Call

CNR-CONACYT 2017-2018

Department

Biology, agriculture and food sciences

Thematic area

Biology, agriculture and food sciences

Status of the project

New

Research proposal

Plants use volatile organic compounds (VOC) to communicate with enemies and friends. Hundreds of examples of direct interactions between plants and their hosts have been described, where VOC act either as repellents or as attractive cues (Holopainen and Gershenzon 2010). More subtly, VOC may trigger indirect protection of plants, attracting carnivore "bodyguards" that feed on herbivores infesting the plant. These tritrophic or multitrophic interactions have been also widely described (Dicke et al. 2009). A final level of interaction may occur between plants that have been infested by pests or pathogens and their healthy neighbors, as the latter (the "receivers") may "eavesdrop" VOC emitted by infested plants, and arm their defense arsenal against the likely forthcoming attack (Heil and Karban 2009). This elusive communication is difficult to track, as eavesdropping may not involve changes in the physiology of "receivers" that are measurable "in vivo", and may only be seen as a priming of defensive biosynthetic pathways.
VOC-mediated interactions may be also triggered, or modulated, by organisms that are beneficial for plants, e.g. mycorrhizal symbioses or soil fungi. We hypothesize that such interactions may render plants more resistant to biotic stressors, thus reducing the emission of VOC induced by pests or pathogens. However, beneficial organisms may trigger their own VOC blend, or alter the blend induced by the stressor. The impact of such multitrophic interaction of plant-plant communication is largely unknown and needs to be investigated. Knowledge of VOC functions in plants may offer important insights on mechanisms of resistance against biotic and abiotic stressors (Loreto and Schnitzler 2010), and on the use of VOC in agricultural practices for integrated pest management( e.g. intercropping VOC emitters and receivers or using "push-pull" approaches) (Hassanali et al. 2008).
Studies performed by the applying research groups have highlighted the involvement of VOC in mechanisms of resistance to stress. In particular, the Mexican team has discovered that a cultivar (cv) of bean (Phaseolus vulgaris) resistant to the fungus Colletotrichum lindemuthianum caused airborne 'associational' resistance to C. lindemuthianum in neighboring susceptible bean plants. This effect was attributed to fungistatic VOC emitted by the resistant cv, and to the priming of resistance gene expression in the normally susceptible cv (Quintana-Rodriguez et al. 2015). The Italian team has found that association of tomato (Lycopersicon esculentum) roots with the beneficial soil fungus Trichoderma longibrachiatum induced a resistance response to pathogens, due to T. longibrachiatum antagonistic activity against other microbes and to a transcriptional re-programming of the plant (De Palma et al., 2016), associated with a modification of tomato VOC emission (Battaglia et al. 2013).
In the present project, we plan to focus on bean (susceptible and resistant cultivars)/C. lindemuthianum interaction as model system. Integrating our technical and scientific skills we will investigate the chemical and molecular mechanisms underlying the observed resistance phenotypes. Moreover, we will broaden the two-species system, including specific Trichoderma isolates in a multitrophic interaction with bean and Colletotrichum. This approach will help understanding whether plant VOC emission, and consequently pathogen resistance, is further modulated by Trichoderma, as already found in tomato. Effects will be evaluated both in treated and neighboring plants of the susceptible and resistant cv. Methodologically, we will use high-resolution proton transfer reaction mass spectrometry (PTR-QiTOF, available at CNR-IPSP) for highly sensitive, real-time detection of the volatile metabolome emitted during the Trichoderma 6 Phaseolus 6 Colletotrichum interaction, in order to precisely identify the activation and modulation of the emission of those VOC that confer associational resistance to neighboring plants. The interaction will be then studied with a genomic approach, analyzing different genotypes and kinships by using a family-based experimental design. Moreover, with a transcriptomic approach, we will analyze gene pathways modification during the multitrophic interaction.
The collaboration between the two research groups (CNR-CONACYT) having complementary expertise will guarantee the harmonization of different techniques in order to obtain a comprehensive analysis of multitrophic interaction between bean plants, T. longibrachiatum, and C. lindemuthianum, to acquire innovative knowledge for the development of new improved beans cvs for application in Integrate Pest Management (IPM) strategies.

References

Battaglia D et al. (2013) Mol Plant-Microbe Int. http://dx.doi.org/10.1094/MPMI-02-13-0059-R
De Palma M., et al. (2016). J Plant Physiol. 2016 Jan 15;190:79-94. doi: 10.1016/j.jplph.2015.11.005.
Hassanali A et al. (2008) Phil. Trans. R. Soc. B 363:611-621
Dicke M, Van Loon JJA, Roxer S (2009) Nature Chem Biol. doi:10.1038/nchembio.169
Heil M, Karban R (2009) Trends Ecol Evol. doi:10.1016/j.tree.2009.09.010
Holopainen J, Gershenzon J (2010) Trends Plant Sci. doi:10.1016/j.tplants.2010.01.006
Loreto F, Schnitzler J (2010) Trends Plant Sci. doi:10.1016/j.tplants.2009.12.006
Quintana-Rodriguez et al. (2015) J. Ecol. doi: 10.1111/1365-2745.12340

Research goals

Objective of the project is to provide genomic, physiological and ecological knowledge for exploiting plant VOC in direct and indirect protection against biotic and abiotic stressors and for future biotechnological work aiming at producing disease- and climate-proof crops
Hypotheses and tests: 1)As general rule, "good emitters are bad receivers" so, the VOC-mediated stress warning is better perceived by plants with alternate capacity to emit volatiles. 2)Trichoderma improves the physiological status of bean plants, namely water relations and primary (photosynthesis) metabolism and modifies the share of carbon allocated to defense as secondary metabolites (carotenoids, phenylpropanoids). 3)The colonization of roots by Trichoderma alters VOC emission by both healthy and Colletotrichum-infected bean plants; in particular, plants colonized by Trichoderma are expected to produce less VOC and to delay VOC induction when challenged by the biotic stressor. 4)Trichoderma-mediated changes in VOC emission by bean alter resistance to Colletotrichum in the emitter, and signaling and priming of defense in neighboring plants. 5)Transcriptomic changes will occur in plants subjected to multitrophic interaction. 6)Characterization of Trichoderma VOC, and evaluation of their potential effects on bean plants, to be used for future application in IPM. 7)Identification of hereditary bases for VOC emitters/receivers for developing breeding programs to improve biotic and abiotic resistance.

Last update: 20/04/2024