Transient expression of genes coding for the poly-gamma-glutamate (gamma PGA) synthetase system (pgs) was investigated in tobacco plants. Three genes of the pgs, pgsA, pgsB and pgsC, were separately placed under the control of the CaMV 35S promoter and introduced into tobacco leaves via Agrobacterium infection. Synthesized gamma PGA in plant tissues was detected immunologically with mouse anti-gamma PGA antiserum which specifically reacts with gamma PGA on a nitrocellulose membrane. Confirmation of gamma PGA biosynthesis in the transient expression analysis in tobacco tissue indicates that subunits of pgs complex were expressed and reassembled in a functional form.