Expansions of key protein families in the German cockroach highlight the molecular basis of its remarkable success as a global indoor pest

The German cockroach, Blattella germanica, is a worldwide pest that infests buildings, including homes, restaurants, and hospitals, often living in unsanitary conditions. As a disease vector and producer of allergens, this species has major health and economic impacts on humans. Factors contributing to the success of the German cockroach include its resistance to a broad range of insecticides, immunity to many pathogens, and its ability, as an extreme generalist omnivore, to survive on most food sources. The recently published genome shows that B. germanica has an exceptionally high number of protein coding genes. In this study, we investigate the functions of the 93 significantly expanded gene families with the aim to better understand the success of B. germanica as a major pest despite such inhospitable conditions. We find major expansions in gene families with functions related to the detoxification of insecticides and allelochemicals, defense against pathogens, digestion, sensory perception, and gene regulation. These expansions might have allowed B. germanica to develop multiple resistance mechanisms to insecticides and pathogens, and enabled a broad, flexible diet, thus explaining its success in unsanitary conditions and under recurrent chemical control. The findings and resources presented here provide insights for better understanding molecular mechanisms that will facilitate more effective cockroach control.We thank the Deutsche Forschungsgemeinschaft for providing funding for this research to M.C.H. via grant BO2544/11‐1 to E.B.B., and acknowledge United States National Science Foundation grant IOS1557864 to C.S. X.B. & M.‐D.P. were supported by the Spanish Ministry of Economy and Competitiveness (grants CGL2015‐64727‐P to X.B. and CGL2016‐76011‐R to M.‐D.P., both with FEDER funds) and Catalan Government (grant 2017 SGR 1030).Peer reviewe