The Effects of Ageing upon α-Amylase Production and Protein Synthesis by Wheat Aleurone Layers

Abstract

Ageing of wheat seed (Triticum aestivum var. Galahad, 1986 harvest) during storage is accompanied by an increase in the proportion of abnormal seedlings produced when aged seed lots germinate. Wheat seed which germinated normally showed a marked increase in total α-amylase activity in aleurone layers between 3 and 6 d of germination. This increase did not occur in the abnormally germinating seeds at any point up to 12 d germination. The reduced capacity for α-amylase synthesis in the abnormal germinators was not due to a decreased protein synthetic capacity of the aleurone layers. [35S]methionine labelling of aleurone proteins followed by isoelectric focusing and SDS-PAGE revealed that at 3 d germination aleurone layers from both normally and abnormally germinating seeds synthesized high pI isoforms of α-amylase. At 6 d germination aleurone layers from normally germinating seeds synthesized both high and low pI isoforms of α-amylase, whilst aleurone layers from abnormally germinating seeds synthesized the high pI isoforms only, but at a reduced rate compared with normally germinating seeds. Lesions arising in the aleurone layer of aged seeds in addition to those found in embryo tissue may have a significant role to play in loss of seed viability during storage.