We tested the expression of the cucumber expansin gene in several heterologous systems including Escherichia coli and transient Nicotiana benthamiana leaves with limited success. We also had limited success in transiently expressing an alternative expansin gene from bamboo in N. benthamiana leaves. In order to determine if expansin over-expression is limited to a seed system, Arabidopsis thaliana seeds were tested. Although all positive and negative controls behaved as expected, none of these common systems expressed the expansin gene well.
Over-expression of cucumber expansin in three heterologous systems, E. coli, transient tobacco leaves, and Arabidopsis seeds was unsuccessful. The cause of this failure is not known. These results confirm the necessity of experimentally exploring several heterologous systems for protein production in order to find one with utility.