Researchers have identified a trimer complex, TaNF-Y, that can simultaneously regulate the biosynthesis of starch and seed storage proteins in wheat, offering a solution to the long-standing challenge of balancing grain yield and quality.
Striking a Perfect Balance
Grain yield (quantity) and grain quality (quality) are two of the most intractable trait complexes, which have been the focus of wheat breeding efforts. Starch is directly related to grain weight, and native seed storage protein (SSP) content and composition have a major impact on flour quality.
Yet a team of researchers from the Chinese Academy of Sciences have now created a set of coordinating tools which could unlock new ways to control both at once, under the direction or Professor Xiao Jun. This suggests that TaNF-Y, as a trimer complex, could coordinate the mesh of starch and SSP biosynthetic pathways to ensure crosstalk among cell compartments and between sucrose interconversion and OA metabolism in wheat grains.
The Trimer Complex Maestro
The TaNF-Y trimer complex consists of three subunit combinations: TaNF-YA3-D, TaNF-YB7-B, and TaNF-YC6-B. The three modules regulated the transcription of SSP and starch through the direct or indirect regulation in these components using their corresponding transcript profiles.
The researchers further used RNAi interference to silence the TaNF-YA3 and TaNF-YC6 genes and subsequently observed that both starch content was reduced, while storage protein content increased. Subsequent study unveiled that the TaNF-Y trimer complex can directly target to TaLMW-400 and TaGli-γ-700 through recruiting Polycomb Repressive Complexes 2 (PRC2) on these gene loci, adding H3K27me3 modification and repressing the transcription of SSP-encoding genes, as well as negative regulator of starch synthesis related gene copy number variation (CNV), TaNAC019.
These results reveal how wheat SSP and starch accumulation are balanced by both direct regulation of SSP level and indirect control of starch synthesis, respectively, allowing the TaNF-Y complex to regulate these two key traits for grain quality and yield simultaneously.
Conclusion
The identification of the TaNF-Y trimer complex providing a direct link between grain yield and quality in wheat, is an important advance. It acts in a well-integrated manner on SSP biosynthesis and influences starch accumulation indirectly, which opens the horizon for breeders to improve both production (quantity) and quality of wheat using this genetically complex, thereby benefitting farmers by increased grain yield as well as consumers through a greater availability of more nutritious food.
