Ribonuclease activity in the developing seeds of normal and opaque-2 maize

Area of Science:

• Plant Molecular Biology
• Biochemistry
• Genetics

Background:

• The opaque-2 gene in maize (Zea mays) is known to influence endosperm development and composition.
• Ribonucleases (RNases) play crucial roles in RNA metabolism and degradation during plant development.

Purpose of the Study:

• To investigate the impact of the opaque-2 mutation on ribonuclease activity in developing maize endosperm and embryos.
• To determine the specific type of ribonuclease responsible for observed activity changes.

Main Methods:

• Comparative analysis of ribonuclease activity in endosperm and embryos of maize homozygous for the opaque-2 gene versus normal maize.
• Assay of ribonuclease activity at different developmental stages post-pollination.
• Analysis of ribonuclease activity ratios at different pH levels (pH 6.0: pH 5.2) to identify specific enzyme contributions.

Main Results:

• Maize endosperm homozygous for the opaque-2 gene exhibited significantly earlier and higher ribonuclease activity, peaking around sixfold higher than normal endosperm between 22-25 days after pollination.
• Heterozygotes showed no comparable increase in endosperm activity.
• The increased activity in opaque-2 endosperm was attributed solely to ribonuclease A, as the activity ratio at different pH levels remained unchanged.

Conclusions:

• The opaque-2 mutation dramatically enhances ribonuclease A activity specifically in the maize endosperm during development.
• While opaque-2 affects the timing and level of ribonuclease activity in the endosperm, embryo ribonuclease activity shows a faster initial increase but reaches the same final level as in normal embryos.