Combating Striga

​Root parasitic plants, such as the witch weed Striga spp. [S. hermonthica (Del.) Benth. and S. asiatica (L.) Kuntze] and the broomrape Orobanches of the Orobanchaceae family, are a major agricultural pest that is considered as one of the seven greatest biological constraints to food production, causing large yield losses in many crops including corn, millet, sorghum, legumes, rapeseed, and tomato. Striga and Orobanche seeds germinate only in the presence of host plants that release strigolactones into the soil, which are required as germination stimulants. Following germination, seedlings develop haustoria that connect them to the vascular tissues of the host and enable the uptake of phytosynthates, minerals and water. This connection is essential for the survival of these obligate parasites that will then grow, bloom and set enormous numbers of seeds at the cost of the host plant (s. picture). Deployment of control strategies that reduce the parasite seed bank and at the same time minimize host-plant root infection are likely to be the most promising control option. In this project, we aim at developing synthetic strigolactone-analogues that can be used to induce the so called “suicidal germination”, i.e. germination in the absence of host plants. Deployment of this strategy that reduces the parasite seed bank in the soil is one of the most promising control options.

​Strigolactones (SLs) are a novel plant hormone and that shapes shoot and root architecture according to nutrient availability. SLs regulate shoot branching, growth of different root types, secondary growth and scenescence. In addition, SLs are released by plant roots into the rhizosphere where they mediate first steps in establishing symbiosis with beneficial mycorrhizal fungi. However, they are also perceived by seeds of root parasitic weeds as germination signal that initiate the infestation of host plants by these pest. There are around 18 known natural sSLs supposed to arise from carlactone, an intermediate connecting the carotenoid precursors with the cannonical SLswith the typical 4 ring structure. We want to understand the mechanism of the reactions leading to the formation of carlactone, i.e. the carotene isomerzation and the combined reactions catalyzed by the carotenoid cleavage dioxygenase 8. Furthermore, we aim at the elucidation of further steps in the biosynthesis and of the biological background of the diversity of SLs. We are also focusing on the role of SLs in the response of plants to drought and heat stress, as indicated by different drought sensitive mutants affected in SL biosynthesis and signaling.