By promoting cell wall loosening,expansins contribute to cell enlargement during various developmental processes.Nevertheless,the role of expansins in the expansion and development of endosperm—a major seed component whose cell size is significantly associated with grain yield—is poorly understood.To explore associated biological processes and the evolution of expansins in maize,we performed a systematic analysis of the expansin gene family and the function analysis of endosperm specificity expression ZmEXPB13.