Amylolytic activity in germinated Agrostemma githago L. seeds

Area of Science:

• Plant physiology
• Seed germination
• Biochemistry

Background:

• The perisperm of Agrostemma githago seeds stores significant starch reserves (40% of dry weight).
• Starch breakdown is crucial for seed germination and seedling development.

Purpose of the Study:

• To investigate the enzymatic mechanisms and developmental regulation of starch degradation in Agrostemma githago seeds.

Main Methods:

• Monitoring starch breakdown over time after imbibition.
• Enzyme activity assays for alpha-amylase, beta-amylase, and maltase.
• Isoelectric focusing to analyze amylase isoenzymes.
• Investigating the effect of exogenous starch on enzyme secretion.

Main Results:

• Starch reserves were significantly degraded between 48 and 96 hours post-imbibition.
• Cotyledons secreted alpha-amylase, while beta-amylase and maltase appeared to originate in the perisperm.
• Alpha-amylase secretion by cotyledons was independent of exogenous starch, indicating an endogenous developmental trigger.
• Secreted alpha-amylase consisted of two isoenzymes, with other starch-degrading isoenzymes remaining within the cotyledons.

Conclusions:

• Starch degradation in Agrostemma githago seeds involves a coordinated enzymatic process with contributions from both the embryo (cotyledons) and the perisperm.
• The secretion of alpha-amylase is an internally regulated developmental event of the embryo.
• Distinct isoenzyme profiles exist between secreted and intracellular starch-degrading enzymes.