Phytase expression in transgenic soybeans: stable transformation with a vector-less construct.

A minimal linear gene cassette (35S-phytase gene-nos) with T-DNA borders was acquired by PCR and directly introduced into soybean through the pollen tube pathway. A total of 13% of T(1 )plants were positive for phyA by specific PCR. Southern blot analyses showed that phyA insertions were harbored stably in T(2) progeny. Phytase expression level increased 2.5-fold over a 6-week period; its highest activity was 150 U/mg protein, compared to 56 U/mg protein in untransformed controls. Activity of phytase increased to 125 FTU/kg in T(3) transgenic seeds as compared to 64 FTU/kg in wild-type plants.