The winter flounder AFP, with codon usage frequencies consistent with those of higher plants, was also used to successfully transform potato using Agrobacterium mediated transformation. Inclusion of a native signal peptide directed the expressed protein to the apoplast. Electrolyte leakage tests (LT50 ) were used to determine the efficacy of the expressed AFP. Leaves from wild-type Russet Burbank potato
and transformed lines expressing varying levels of AFP were tested for damage after being held
for 30 min at temperatures between −2 and −4 ◦ C. Freezing was
induced by the application of external ice. The wild-type plants
exhibited an LT50 of −2.5 ◦ C while transformed lines expressing
AFP exhibited a range of lower LT50 values depending on the level
of AFP production. The line expressing the most AFP exhibited an
LT50 of −3.5 ◦ C, indicating that the AFP provided approximately 1 ◦ C
of protection relative to the wild-type.