Planck-Gesellschaft). I thank Prof. Dr. Ronald Kühnlein for offering me such a great chance to do my PhD study at MPIbpc. I thank Prof. Dr. Herbert Jäckle for the wonderful fruit fly and biology research facility, Coffee, last half-year financial support, and considerate advice.Especially, I would like to thank Prof. Dr. Ronald Kühnlein. His continuous supports enabled me to finish the dissertation. Numerous discussion, emails, and comments guided and inspired me to do critical thinking, and to carry out the project in a better way. I am very grateful to other two members of my thesis advisory committee: Prof.