Amylases in developing barley seeds

Area of Science:

• Plant Biochemistry
• Enzymology
• Seed Development

Background:

• Amylases are crucial enzymes in starch metabolism during seed germination and development.
• Understanding amylase profiles in barley (Hordeum vulgare L.) is key to optimizing malting and brewing processes.

Purpose of the Study:

• To characterize the temporal and spatial expression of amylolytic enzymes in developing barley seeds.
• To investigate the influence of maturation, gibberellic acid, and calcium on amylase activity and electrophoretic profiles.

Main Methods:

• Colorimetric assays to measure total amylolytic activity.
• Electrophoresis (PAGE) to separate and identify different amylase isoforms.
• Enzyme treatments (papain) to further characterize amylase forms.

Main Results:

• Peak amylase activity was observed in aleurone layers and starchy endosperm at 5 and 20 days post-anthesis.
• Early aleurone layers showed four alpha-amylase bands; mature seeds exhibited seven medium-mobility bands, also found in the starchy endosperm.
• Immature aleurone layers did not respond to exogenous gibberellic acid, while mature aleurone layers did.
• Calcium influenced the electrophoretic mobility and activity of specific amylase bands during endosperm maturation.
• Papain treatment of immature starchy endosperm revealed four beta-amylase forms.

Conclusions:

• Barley seed amylase composition undergoes significant changes during development, involving shifts in alpha-amylase isoforms.
• Gibberellic acid's role in amylase induction appears specific to mature aleurone layers.
• Calcium plays a role in regulating amylase activity during starchy endosperm maturation.
• Distinct alpha- and beta-amylase forms are present at different developmental stages and tissues.