PhD defence - Jincheng Shen
Exploring insect-deterrence mechanisms mediated by saponins in the non-model plant Barbarea vulgaris.
Assessment committee
- Chairperson: Deyang Xu, PLEN, University of Copenhagen
- Martin Hansen, DTU Sustain
- Nicole van Dam, Leibniz Institute / iDiv, Friedrich Schiller University Jena
Supervisors
- Principal supervisor: Søren Bak, PLEN
- Co-supervisor: Pablo D. Cárdenas, PLEN
Department
Department of Plant and Environmental Sciences (PLEN)
Place
'Festauditoriet', A1.01, Bülowsvej 17, Frederiksberg
Ask for a copy of the thesis here: bak@plen.ku.dk
Abstract
Plant–insect coevolution has been a major driver of specialized metabolite diversification, yet the genetic basis of natural variation in defensive chemistry remains poorly understood. Using the non-model crucifer plant Barbarea vulgaris, this thesis links gene function to ecological defense in triterpenoid saponins. Our results provide direct in planta evidence that LUP5 is a key determinant of natural variation in insect resistance in B. vulgaris, underscoring the pivotal role of the saponin backbone in herbivore deterrence. By linking promoter activity to metabolite structural diversity, this work provides mechanistic and conceptual insight into how plants coordinate specialized metabolism and defense. Through comparative transcriptomics, we identified fifteen glycosyltransferase candidates, providing valuable molecular tools for dissecting how glycosylation patterns shape saponin structures and their bioactivity. Finally, we demonstrated that glycosylation patterns are a key determinant of both insect defense activity and their biotransformation in insects during digestion. Together, this study demonstrates that β-amyrin biosynthesis, promoter regulation, and glycosylation collectively determine the defensive function and ecological fate of saponins, and highlights that insect metabolism adds a further layer of complexity for our general understand of saponins´ role in plant defense.