Correlation between heterologous expression and zeocin resistance for the four different aquaporins. Western blot with crude cell extract from five representative clones from each zeocin selection level (100, 500 or 1000 μg zeocin/mL) and each aquaporin isoform (HsAQP8, HsAQP5, SoPIP1;2 and AtSIP1;1). HsAQP8 samples (top) show the characteristic aquaporin pattern with monomer, dimer, trimer and tetramer and also indicate that degradation seems to occur. For simplicity only the major band, corresponding to the monomer, is shown for the other aquaporins. (Asterisks indicate clones carrying the SoPIP1;2 construct recovered from selection at 2000 μg zeocin/mL). There is a correlation between recombinant aquaporin expression and level of antibiotic resistance.