Ribosome biogenesis is a fundamental cellular process in eukaryotic cells.Impaired ribosome biogenesis causes developmental defects;however,its molecular and cellular basis is not fully understood.We cloned a gene responsible for a maize small seed mutant dek*,and found it encodes Ribosome export associated 1(ZmRea1).Rea1 is an AAA-ATPase that control 60S ribosome export from the nucleus to the cytoplasm after ribosome maturation.