Sugar mimics the light-meditated β-amylase induction and distribution in maize and pearl millet leaves

Abstract

In the first leaf of dark-grown maize (Zea mays) and pearl millet (Pennisetum americanum) seedlings, β-amylase activity increased from the leaf base to the tip. Seedlings grown under continuous red light possessed several folds higher β-amylase activity compared with dark-grown leaves. The exposure of dark-grown seedlings to red light for 12-24h also enhanced β-amylase activity in leaf. Exposure to light altered the β-amylase distribution in leaf, resulting in higher β-amylase activity in the region close to the leaf base, which gradually declined towards the tip. Protein blotting revealed that the distribution of β-amylase activity corresponded with the distribution of β-amylase protein. The excision of the leaves of both of the species at the base did not affect the distribution of β-amylase in both dark- and light-grown leaves. On supplying sugar to the base of excised dark-grown leaves, β-amylase distribution in the leaf shifted to a profile similar to the light-grown leaves. In excised light-grown leaves, sugar further stimulated β-amylase activity; however, the β-amylase distribution profile of light-grown leaves was retained. These results indicate that light and sugars share common elements in the signal pathway regulating β-amylase activity.