Ribonuclease Activity in Normal, opaque-2, and floury-2 Maize Endosperm during Development

Area of Science:

• Plant molecular biology
• Maize genetics
• Biochemistry

Background:

• The opaque-2 mutation in maize (Zea mays L.) is known to affect endosperm protein composition, particularly zein synthesis.
• Understanding the molecular mechanisms underlying these changes is crucial for improving maize quality and yield.

Purpose of the Study:

• To investigate the effect of the opaque-2 mutation on ribonuclease activity and accumulation in maize endosperm.
• To determine the dominance pattern of the opaque-2 mutation concerning ribonuclease activity.
• To explore potential links between ribonuclease accumulation and other endosperm proteins.

Main Methods:

• Enzyme assays were performed to measure ribonuclease activity in maize endosperm at different developmental stages.
• Ribonuclease accumulation rates were quantified in different maize inbred lines and genetic backgrounds.
• Dosage series experiments were conducted to assess the recessivity of the opaque-2 mutation.

Main Results:

• Homozygous opaque-2 significantly elevated ribonuclease accumulation rates in W64A maize endosperm before 16 days post-pollination.
• After 16 days, ribonuclease accumulation rates in opaque-2 and normal maize were similar, suggesting a transient effect of opaque-2.
• The opaque-2 dosage series indicated that the mutation is not fully recessive regarding ribonuclease activity.
• The floury-2 mutation did not affect ribonuclease accumulation in the B14 inbred line.

Conclusions:

• The opaque-2 mutation in maize enhances ribonuclease accumulation early in endosperm development, impacting enzyme activity.
• The genetic control of ribonuclease accumulation by opaque-2 is not completely recessive.
• These findings provide insights into the pleiotropic effects of opaque-2, potentially influencing other endosperm proteins like zein.