Improved plant-based production of E1 endoglucanase using potato: expression optimization and tissue targeting

Optimization of Acidothermus cellulolyticus endoglucanase (E1) gene express ion in transgenic potato (Solanum tuberosum L.) was examined in this study, where the E1 coding sequence was transcribed under control of a leaf speci fic promoter (tomato RbcS-3C) or the Mac promoter (a hybrid promoter of man nopine synthase promoter and cauliflower mosaic virus 35S promoter enhancer region). Average E1 activity in leaf extracts of potato transformants, in which E1 protein was targeted by a chloroplast signal peptide and an apopla st signal peptide were much higher than those by an E1 native signal peptid e and a vacuole signal peptide. E1 protein accumulated up to 2.6% of total leaf soluble protein, where E1 gene was under control of the RbcS-3C promot er, alfalfa mosaic virus 5'-untranslated leader, and RbcS-2A signal peptide . E1 protein production, based on average E1 activity and E1 protein accumu lation in leaf extracts, is higher in potato than those measured previously in transgenic tobacco bearing the same transgene constructs. Comparisons o f E1 activity, protein accumulation, and relative mRNA levels showed that E 1 expression under control of tomato RbcS-3C promoter was specifically loca lized in leaf tissues, while E1 gene was expressed in both leaf and tuber t issues under control of Mac promoter. This suggests dual-crop applications in which potato vines serve as enzyme production 'bioreactors' while tubers are preserved for culinary applications.