In the department of Plant Physiology we aim to elucidate plant-signal transduction pathways employed in biotic interactions, focussing on the role of plant metabolites. We research perception and signaling mechanisms during plant-insect interactions. In my research we study the defence against pest-insects via the production of specialised metabolites with tomato and whitefly as model species. The lab combines metabolomics, transcriptomics and genome information with phenotypic responses. We make use of the natural variation found in ancestral/ wild tomato accessions to identify metabolites, genes and regulatory elements and try to apply this knowledge to reconstruct defence pathways in cultivated tomato.
Worldwide, insects and viruses cause enormous losses in crop production. Much like what we currently experience, crops are hit with virus infections often transmitted by vector insects such as whiteflies and thrips. Such infestations threaten food production worldwide, a problem only amplified by global warming. Conventional control of vector insects is difficult. Yearly 3.5 million tons of pesticides are applied globally. Theses pesticides are often persistent in the environment and harm off-target organisms, pollution ground- and surface waters. Many (wild) plant species have evolved (chemical) insect defences that can be explored as alternatives to the use of persistant insecticides, mechanisms that can be re-introduced in defenceless cultivars.
Wild tomatoes produce a wide variety of defence-related metabolites, termed specialised metabolites. Estimates on the divergence of specialised metabolites reach over 200.000 different structures, including flavonoids, acylsugars, alkaloids and a huge variety of terpenoids (isoprenoids). The latter are among the most reported bioactive compounds in relation to insects.
Combining resistance assays with a metabolomics approach we identified the sesquiterpene 7-epizingiberene and its dehydrogenated derivative R-curcumene from the wild tomato Solanum habrochaites to repel the silverleaf whitefly Bemisia tabaci, a potent vector of Geminiviridae (Bleeker et al., 2009, 2011). Transcriptomics of a range of wild accessions next led to the identification and characterisation of the two genes underlying the biosynthesis of 7-epizingiberene (i.e. ShzFPS and ShZIS) in wild tomato which were consequently introgressed in a cultivated background (Bleeker et al., 2012).
We however also observed low survival rates of whiteflies on the leaf surface of S. habrochaites, which led to the hypothesis that the volatile sesquiterpenes must signal the presence of a (related) toxic compound, hence triggering the repellence response. As metabolic profiles are complex mixtures we developed a customised Random Forest learning algorithm to predict specialised metabolites that can explain the resistance phenotype (Kortbeek, Galland et al., 2021). Using this feature selection approach we predicted that in our S. habrochaites, an alcohol derivative of 7-epizingiberene, present on the leaf surface, is causal to the whitefly toxicity phenotype.
Recently, the P450-enzyme involved in oxidation of the volatile 7-epizingiberene to two compounds, 9-hydroxy-zingiberene and 9-hydroxy-10,11-epoxyzingiberene was identified (Zabel et al., 2021) and its activity thoroughly investigated. We showed that especially the latter sesquiterpene-derivative exhibits toxicity against whitefly.
regulation and secretion
Plants often produce and store defence metabolites in specialised structures. In tomato anti-insect metabolites are mostly produced in specialised glandular hairs called trichomes. These are like biochemical factories, present on the surface of green tissues. Type-VI trichomes of tomato consist of a secretory cavity surrounded by four metabolically acitve secretory cells. Within the Plant Physiology department we are interested in investigating these tomato glandular trichomes, their content, the factors that govern their development, the storage ability and the transport of metabolites.
The biosynthesis of defence compounds is costly and therefore under tight regulation. Whereas the biosynthetic genes for the production of terpenes are now largely identified, less is known about the regulation of the terpene biosynthetic pathways in tomato trichomes. Several transcription factors involved in metabolite production and for the presence of glandular trichomes have been identified over recent years. The lab of Robert Schuurink identified keyplayer MYC1, a trancription factor instrumental for the presence of type VI glandular trichomes on tomato (Xu et al., 2018).
translation of research
To re-introduce natural resistance, knowledge on the biosynthetic pathways and how these are regulated is essential. Using an -omics approach in combination with the natural variation in metabolite production and insect resistance found in wild ancestors, we aim to identify limiting factors in sustainable natural insect resistance. Through close collaboration with partners in the Agro-industry, we are able to translate our research findings and benefit the development of a novel generation of crops with increased pest-insect resistance and a significantly reduced dependency on chemical application.
the above is part of the research taking place in the department of Plant Physiology, headed by Prof. dr. Michel Haring, together with dr. Robert Schuurink, dr. Silke Allman and Pulu Sun. Our department is member of the research theme Green Life Sciences (GLS) within the Swammerdam Institute for Life Sciences (SILS).
GLS consists of five complementary disciplines: Plant Physiology (PP), Molecular Plant Pathology (MPP), Plant Cell Biology (PCB), Plant Hormone Biology (PHB) and Plant Development & (Epi)Genetics (PDEG). Next to research collaborations, GLS researchers are active in the education program of the MSc track Green Life Sciences (MSc Biological Sciences) of our Faculty of Science. GLS participates in the Dutch graduate school Experimental Plant Sciences (EPS), a training and network platform for the PhD students and postdocs.
Ruy Kortbeek, PhD candidate. Defence in the wild; from trichome transcriptomes and metabolomes to breeding tools for defence markers in tomato. NWO TTW-VIDI
Marc Galland, Data Scientist & former Post-Doc. Defence in the wild; from trichome transcriptomes and metabolomes to breeding tools for defence markers in tomato. NWO TTW-VIDI. Rearm cultivated tomato with natural and durable resistance mechanisms from wild tomato. EU-Marie Curie. Founder and Lead of the Science Park Study Group (link).
Michelle van der Gragt, PhD candidate. Master old resistance in new tomatoes: transcriptional control of metabolite production by small RNAs. NWO-Groen.
Rodrigo Therezan de Freitas, Post-Doc. Optimization of terpenoid production in cultivated tomato through identification of novel wild-tomato genetic factors. TKI-U.
Lissy-Anne Denkers, PhD candidate. Insight on the inside: exploring natural variation in phloem-based metabolites for insect resistance. NWO-LIFT
Sofia Maia Pinto, MSc internship
Former group members
Aleksandra Muras, technician (BASF)
Maurice Heilijgers, technician (Rijk Zwaan)
Former Students (MSc, BSc)
Michelle Zwart, UvA MSc Biological Sciences track Green Life Science (2021)
Kamiel Blok, UvA BSc Biology (2021)
Jolanta Szkodon, VU-UvA MSc Bioinformatics and Systems Biology (2020)
Sjors Huizinga, UvA BSc Biology (2020)
Wicher Otten, VU-UvA MSc Bioinformatics and Systems Biology (2019-2020)
Lisette van Brakel, UvA MSc Biological Sciences track Green Life Science (2019)
Lennart Lambalk, UvA BSc Biology
Sanne Ypenburg, UvA MSc Biological Sciences (2017)
Lisa Govers, VU, BSc Biology (2017)
Miguel van der Wolf, UvA BSc Biology (2016)
Frederike Klein, UvA BSc Chemistry (2016)
Felix van Leuven, UvA BSc Biology (2015)
Maarten Rouwet, WUR MSc Plant Breeding (2014).