Ecology of intraspecific chemodiversity in a metal hyperaccumulator plant

• Applicant: Dr. Rocky Putra
• Subject Area: Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 521193842

Chemical, including meta(loid), contamination has been a major environmental threat globally. However, certain plant species, namely hyperaccumulators, are able to hyperaccumulate and tolerate high concentrations of metal(loid)s from soil. These hyperaccumulator plants can be used to decontaminate metal-polluted areas, known as phytoremediation. Nevertheless, little is understood how these hyperaccumulators interact with the environment. The elemental defence hypothesis postulates that metal hyperaccumulation protects plants against insect and pathogen attacks. In addition to elemental defence, plants produce a plethora of specialised (soluble and volatile) metabolites, which can act as direct and indirect defences toward antagonists. These two types of defences, inorganic and organic, can also be induced following attacks, but the relationship between the two is less explored with regard to the ecology and evolution of metal hyperaccumulation. Likewise, the composition and concentration of both defences can highly differ intraspecifically (within species) and intraindividually (within an individual), adding to the chemodiversity of plants. For example, different populations of Arabidopsis halleri vary in their foliar glucosinolate composition, indicating distinct chemotypes, yet they also hyperaccumulate zinc (Zn) and cadmium (Cd), conferring a potent defence against herbivorous insects. Some other plant species are known to take up and accumulate the metalloid silicon (Si), which has been increasingly reported to ameliorate biotic and abiotic stresses, including heavy metal toxicity. However, the involvement of Si in the context of metal hyperaccumulation, to my knowledge, is still in its infancy. Therefore, this project aims to address the following central questions: • Do soil metal amendment (Zn and Cd) and Si supplementation affect intraspecific and intraindividual chemodiversity, by changing the composition and concentrations of foliar elements and (semi-polar) metabolic fingerprints of different populations and within individuals (e.g. young vs old leaves) in A. halleri? • Does fungal infection impact composition and concentrations of foliar elements, glucosinolates and camalexin (a fungal-induced specialised defence metabolite) in A. halleri populations under such soil metal(loid) treatments? • How do foliar elements and volatiles change in response to fungal and soil treatments intraspecifically between populations of A. halleri? How do these changes in foliar elements and/or specialised metabolites influence fungal growth in vivo and in vitro? By combining chemical analyses of the elementome, metabolome and volatilome with in vivo assays of fungal performance and in vitro bioassay-guided fractionation as well as robust statistical analyses, this project is anticipated to give us a deeper insight into the fascinating ecological aspects of intraspecific chemodiversity in a model hyperaccumulator plant.

• DFG Programme: WBP Position