Plant height influences plant architecture, lodging resistance, and yield performance. It is modulated by gibberellic acid (GA) metabolism and signaling. DELLA proteins, acting as central repressors of GA signaling, integrate various environmental and hormonal signals to regulate plant growth and development in Arabidopsis. We examined the role of two DELLA proteins, GmRGAa and GmRGAb, in soybean plant height control. Knockout of these proteins led to longer internodes and increased plant height, primarily by increasing cell elongation. GmRGAs functioned under different light conditions, including red, blue, and far-red light, to repress plant height. Interaction studies revealed that GmRGAs interacted with the blue light receptor GmCRY1b. Consistent with this, GmCRY1b partially regulated plant height via GmRGAs. Additionally, DELLA proteins were found to stabilize the protein GmSTF1/2, a key positive regulator of photomorphogenesis. This stabilization led to increased transcription of GmGA2ox-7b and subsequent reduction in plant height. This study enhances our understanding of DELLA-mediated plant height control, offering Gmrgaab mutants for soybean structure and yield optimization.

The size and shape of rice grains influence their yield and commercial value. We investigated the role of OsDA1, a rice homolog of the Arabidopsis DA1 gene, in regulating grain size and shape. OsDA1 was highly expressed in young spikelets and glumes. Its overexpression led to enlarged seeds with increased width and decreased length/width ratio (LWR) and knocking out OsDA1 reduced grain width and increased grain length and LWR. A R310K point mutation in the DA1-like domain is a potential target for breeding for increased grain width and length. OsDA1 interacted with TCP gene-family proteins to regulate grain size and shape. Our findings deepen our understanding of the molecular mechanisms underlying grain size regulation and provide useful information for improving grain yield.