SECRETION OF A HEAT-STABLE FUNGAL BETA-GLUCANASE FROM TRANSGENIC, SUSPENSION-CULTURED BARLEY CELLS

Transgenic plant cell cultures have a potential for production and sec retion of important proteins and peptides. To assess the possibilities of using a stable barley suspension culture for secretion of heterolo gous proteins in active form, we expressed the cDNA of the thermostabl e beta-glucanase (EGI) of Trichoderma reesei in barley suspension cell s. The cDNA coding for EGI and its signal sequence was placed under th e control of the CaMV 35S promoter and the construction was transferre d to the cells by particle bombardment. Stably transformed lines were obtained by selecting for a cotransformed antibiotic resistance marker . The expression of EGI cDNA led to accumulation of EGI in the culture medium, as shown by analysis with EGI-specific antibodies. Enzymatic assays confirmed that the EGI secreted by the suspension cells retaine d its activity and thermostable character. Furthermore, it was shown t hat the enzyme produced by the transgenic suspension culture could be used for degradation of soluble beta-glucans during mashing.