A novel in vitro system for gamete fusion in maize.

Various systems by using electric pulse, calcium, or polyethylene glycol have been developed in the past decade for the in vitro fusion of plant gametes. These in vitro systems provide a new way to study the fertilization mechanisms of plants. In this study, we developed a bovine serum albumin (BSA)-mediated fusion system for the in vitro fusion of maize gametes. The in vitro fusion of the isolated single egg cell and sperm cell of maize was observed microscopically in the BSA solution and the fertilized egg cell showed normal cell wall regeneration and nuclear division. The effects of the BSA concentration, pH value and calcium level on the efficiency of the maize gamete fusion were also assessed. BSA concentration and pH value did significantly affect the efficiency of the gamete fusion. Calcium was not necessary for the gamete fusion when BSA was present. The optimal solution for the gamete fusion contained 0.1% BSA, pH 6.0. The fusion frequency was as high as 96.7% in that optimal solution. This new in vitro fertilization system offers an alternative tool for the in vitro study of fertilization mechanisms with much simpler manipulating procedure than PEG system, and it will be especially useful for the in vitro study of the calcium dynamics during plant fertilization.