A Comparison of α-Amylase Isozyme Profiles in Selected Su and High-Sugar Sweet Corn (sh-2, su-1, su-1 se) Lines (Zea mays L.)

Abstract

α-Amylases were purified from germinating starchy (Su) maize kernels (Funks G4646) using glycogen precipitation and preparative SDS-PAGE. Antiserum to the purified α-amylases was produced in rabbits. Isozymes of α-amylase from the scutellum and aleurone tissues of kernels of five Su lines were compared with a sweet corn (su-1) and two high-sugar sweet corn (su-1 se and sh-2) inbred lines in the same genetic background, using isoelectric focusing gels, starch zymograms, and immunoblotting analyses. The most notable differences were found in the high-sugar sweet corn kernels. In the sh-2 aleurone, there were no α-amylase isozymes detected on the zymogram and immunoblot, indicating a lack of enzyme accumulation. In the su-1 se scutellum, there were fewer isozymes compared with most of the lines examined, but the significance of this is not clear. Comparison of the five Su lines revealed several isozymes common to all the kernels examined, but there were considerable tissue-specific differences in the number of isozymes between the aleurone and scutellum tissues. The Funks G4646 (Su) and RB-4 (Su) had similar scutellar and aleurone isozyme patterns, with the aleurone having one more isozyme than the scutellum. In OH43 (Su) kernels, the scutellum had one to two more isozymes with α-amylase activity than the aleurone, while the IL451b (Su) scutellum had fewer isozymes (seven to eight) than the aleurone (14-16). Both high- and low-pI isozymes of wheat and barley, and the low-pI isozymes of rice, were recognized by the antibodies to maize α-amylases developed in this study. These data indicate a complex relationship between the carbohydrate and sugar composition of the kernel and the synthesis of α-amylase isozymes during germination.