Alternative Splicing of Differentially Regulates Grain Weight and Size in Bread Wheat.

The heterotrimeric G-protein mediates growth and development by perceiving and transmitting signals in multiple organisms. Alternative splicing (AS), a vital process for regulating gene expression at the post-transcriptional level, plays a significant role in plant adaptation and evolution. Here, we identified five splicing variants of G subunit gene ( to ), which showed expression divergence during wheat polyploidization, and differential function in grain weight and size determination. overexpression significantly reduced grain weight by 5.89% and grain length by 5.04%, while - overexpression did not significantly alter grain size compared to wild type. Overexpressing significantly increased the grain weight by 5.70% and grain length by 4.30%. Biochemical assays revealed that isoforms (TaGS3.1-3.4) with an intact OSR domain interact with WGB1 to form active G heterodimers that further interact with WGA1 to form inactive G heterotrimers. Truncated isoforms , which lack the C-terminal Cys-rich region but have enhanced binding affinity to WGB1, antagonistically compete with to bind WGB1, while with an incomplete OSR domain does not interact with WGB1. Taking these observations together, we proposed that differentially regulates grain size via AS, providing a strategy by which the grain size is fine-tuned and regulated at the post-transcriptional level.