Efficient expression of green fluorescent protein gene in rice cells

An expression vector suitable for rice (Oryza sativa L.), pAct1.GFP, was constructed by placing the improved green fluorescent protein (GFP) coding sequence under the control of the actin 1 (Act1) promoter of rice. Embryogenic rice calli derived from the mature embryos were bombarded with gold particles coated with pAct1.GFP. Expression of GFP gene in rice cells was followed by incident-light fluorescence microscopy in vivo and in real time. Bright green fluorescence signals were visible under blue light 3 to 4 h following bombardment. After 10 to 16 h, the maximum expression of GFP gene was observed in 85% of the calli. Meanwhile, the expression of beta-glucuronidase (GUS) gene driven by Act1 promoter reached the highest in rice cells 40 to 48 h after transformation. GFP as a sensitive and vital reporter may be used as a replacement for GUS in rice transient expression system. However, no green fluorescence from stable expression of GFP gene was observed in transformants.