Genetic transformation of tropical maize (Zea mays L.) inbred line with a phytase gene from Aspergillus niger.

A full-length cDNA of phyA gene of Aspergillus niger, encoding phytase enzyme, was cloned and expressed in E. coli BL21 cells and assayed for its activity. The phyA cDNA consisted of 1404 bp, which encoded 467 amino acid residues. The phytase activity of purified phytase was 826.33 U/mL. The phyA gene under the control of endosperm-specific promoters was transformed into an Indian maize inbred line, UMI29, using particle bombardment-mediated transformation method to generate transgenic maize plants over-expressing phytase in seeds. PCR and GUS analyses demonstrated the presence of transgenes in T0 transgenic plants and their stable inheritance in the T1 progenies. Three transgenic events expressing detectable level of A. niger phytase were characterized by western blot analysis. Phytase activity of 463.158 U/kg of seed was observed in one of the events, JB-UMI29-Z17/2. The phytase activity of transgenic maize seeds was 5.5- to 7-fold higher than the wild-type UMI29 seeds and, consequently, the seeds had 0.6- to 5-fold higher inorganic phosphorus content.