Elucidation of strigolactone biosynthesis in the host plant rice and the signal perception in the parasitic plant Striga hermonthica

Strigolactones (SLs) are a newly identified class of plant hormones regulating plant architecture, including shoot and root branching. Plants also secrete blends of SLs into the rhizosphere, where they stimulate colonisation of the host roots by arbuscular mycorrhizal (AM) fungi, beneficial organisms for the host. But SLs also induce the seed germination of root parasitic plants, such as Striga, which can have a big negative impact on crop yield. A better insight in how the different SLs are synthesized by the host and how the parasitic plant Striga perceives them could help to develop crops with proper AM colonisation and Striga resistance at the same time. In this thesis, two cytochrome P450 enzymes responsible for the last step in SL formation and SL structural diversification in rice were identified. In addition, the F-Box protein MAX2 of Striga (ShMAX2), a SL signalling component, was characterised, representing the first example from a root parasitic plant species, which is paving the way for furthering our understanding of how SLs are perceived by these parasites. The knowledge gained in this thesis brings us a significant step closer to the possibility to improve crop breeding strategies for parasitic weed resistance.