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PhD Thesis

Responses of Black Nightshade (Solanum nigrum) to insect herbivory with a special focus on the 18-amino acid polypeptide systemin
Friedrich-Schiller-Universität Jena
First Supervisor: Prof. I.T. Baldwin

Using genetically modified plants as a tool to study plant-insect interactions, I am working on the responses of Black Nightshade (Solanum nigrum) to insect herbivory. In particular, my work is focused on the role of the 18-amino acid peptide hormone systemin, which has been shown to play an important role in the wound response of the closely related tomato (Solanum lycopersicum). There, systemin acts at or near the site of wounding by amplifying the jasmonate-derived mobile wound signal. Using plants stably transformed with an inverted repeat prosystemin construct to silence the expression of the systemin precursor (IRSys plants), I was able to demonstrate that systemin does not mediate direct defence responses in S. nigrum as it does in tomato. Instead, it plays a crucial role in tolerating rather than resisting herbivory, which I could show by means of growth- and competition experiments using differently treated (induced by wounding and oral secretions of Manduca sexta larvae or treated with wounding and oral secretions of M. sexta and systemin) wild-type or IRSys plants. By unravelling the ecological function of systemin, I could demonstrate for the very first time after more than one decade of research on systemin an alternative role for this signalling peptide in S. nigrum.