Expression of maize prolamins in Escherichia coli

We have constructed a cDNA expression library of developing corn (Zea mays L.) endosperm using plasmid pUC8 as vector and Escherichia coli strain DH1 as host. The expression library was screened with non-radioactive immunological probes to detect the expression of gamma-zein and alpha-zein. When anti-gamma-zein antibody was used as the probe, 23 colonies gave positive reactions. The lengths of cDNA inserts of the 23 colonies were found to be 250–900 base pairs. When anti-alpha zein antibody was used, however, fewer colonies gave positive reactions. The library was also screened by colony-hybridization with ³²P-labeled DNA probes. Based on immunological and hybridization screening of the library and other evidence, we conclude that alpha-zein was either toxic to E. coli cells or rapidly degraded whereas gamma-zein and its fragments were readily expressed.