Subclass III SnRK2 Kinases Coordinate Starch and Storage Protein Synthesis During Maize Kernel Development

Area of Science:

• Plant Biology
• Molecular Genetics
• Biochemistry

Background:

• Improving maize yield and quality necessitates enhancing both starch and protein accumulation.
• Understanding the integrated regulatory mechanisms of these pathways is crucial for achieving this goal.

Purpose of the Study:

• To identify central regulators orchestrating starch synthesis and storage protein accumulation in maize kernels.
• To elucidate the molecular mechanisms by which these regulators function and their role in kernel development.

Main Methods:

• Analysis of higher-order SnRK2s mutants lacking ZmSnRK2.10.
• Investigating the direct phosphorylation targets of ZmSnRK2.10, including starch synthesis enzymes.
• Examining the modulation of downstream transcription factors (Opaque-2, ZmbZIP75) by ZmSnRK2.10.
• Studying the spatiotemporal activation of ZmSnRK2.10 by sucrose and abscisic acid (ABA).
• Evaluating the effects of ZmSnRK2.10 overexpression on kernel traits.

Main Results:

• Higher-order SnRK2s mutants exhibit defective kernel development with reduced starch and protein content.
• ZmSnRK2.10 directly phosphorylates and enhances the activity of starch synthesis enzymes like Bt1.
• ZmSnRK2.10 indirectly promotes protein synthesis by modulating transcription factors Opaque-2 and ZmbZIP75.
• ZmSnRK2.10 is sequentially activated by sucrose and ABA during kernel development.
• Overexpression of ZmSnRK2.10 significantly increases starch and protein content, improving kernel quality.

Conclusions:

• Subclass III SnRK2s, with ZmSnRK2.10 as a key player, act as central regulators of maize kernel storage functions.
• ZmSnRK2.10 integrates starch and protein accumulation pathways through direct and indirect mechanisms.
• ZmSnRK2.10 provides a potential genetic resource for enhancing maize yield and quality.