1 Structural circuit plasticity by a neurotrophin with a Toll modifies dopamine-dependent behaviour Jun Sun 1 , Suzana Ulian-Benitez 1,2 , Manuel G. Forero 3 , Guiyi Li 1 , Deepanshu Singh 1 , Sebastian Cachero 4 , Francisca Rojo-Cortés 1 , Marta Moreira 1 , Dean Kavanagh 5 , Gregory Jefferis 4 and Alicia Hidalgo 1* 1, Structural Plasticity & Regeneration Group, School of Biosciences, University of Birmingham, UK; 2, current address: Buck Institute for Research on Aging, California, US; 3, Universidad Señor de Sipán, Chiclayo, Perú; 4, MRC LMB, Cambridge, UK; 5, Institute of Biomedical Research, University of Birmingham, UK. *Author for correspondence: 00 44 (0)121 4145416 a.hidalgo@bham.ac.uk Short running title: Novel molecular mechanism of circuit plasticity Keywords: structural brain plasticity, neurodegeneration, neuronal activity, dopamine, neurotrophin, Drosophila neurotrophin 2, DNT-2, Toll, Toll-Like Receptor, Kekkon, Kek, TrkB, TrkB-T1, TrkC-T1