Improving organic phosphate utilization in transgenic white clover by overexpression of Aspergillus niger PhyA gene

Abstract

Using the cotyledon of white clover as explants, the transgenic white clover lines ectopic expression of the PhyA gene were established based on Agrobacterium tumefaciens-mediated transformation method. It was found that the tested transgenic lines were all Polymerase Chain Reaction (PCR) positive. The transgenic lines 1 to 4 were used for further Southern blot and Northern blot analysis. The lines 1 and 3 with higher level of PhyA expression were used to assay the phytase activities in root and its intercellular space. When the phytate was the sole phosphorus source, the phytase activities in root in lines 1 and 3 were 31.43% and 44.76% higher than those in control (CK), respectively. Meanwhile, the phytase activities in the root intercellular space in lines 1 and 3 were 3.3-fold and 5.12-fold higher than those in CK, respectively. The phosphorus concentration of plants, the accumulative P amount per plant, plant fresh weight, and plant dry weight were all much higher in lines 1 and 3 than in CK. Thus, it is clearly shown that ectopic expression of Aspergillus niger PhyA gene could significantly increase the ability for white clover to utilize organic phosphate under inorganic phosphate (P_i)-deficient condition.