Comparative proteomics of orchardgrass reveal the effect of SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 13 on flowering time.

Flowering time in plants is a tightly controlled procedure that influences yield and ensures genetic diversity. Orchardgrass (Dactylis glomerata) is a well-known forage grass widely used for silage, hay, and grazing. To elucidate the regulatory mechanisms underlying flowering in orchardgrass, this study conducted a comparative proteomic analysis of the early-flowering Baoxing and the late-flowering Donata cultivars across three developmental stages. Notably, the alpha-linolenic acid metabolism flux was down-regulated in Baoxing during the vernalization stage. Moreover, the expression level of the SQUAMOSA PROMOTER BINDING PROTEIN-LIKE protein DgSPL13 was markedly decreased in the Baoxing cultivar relative to the Donata cultivar during and after the vernalization stage. However, overexpression of DgSPL13 in Arabidopsis promoted early flowering. Dual-luciferase assays revealed that DgSPL13 enhances the expression of the VERNALIZATION gene DgVRN1 through promoter binding under normal conditions, but not under cold conditions. The increased expression of DgSPL13 during the vegetative growth stage compared to the vernalization stage implies that timely expression of DgSPL13 is crucial for activating DgVRN1 expression and promoting flowering in orchardgrass. This investigation enhances the comprehension of the molecular regulation of flowering and offers valuable insights into orchardgrass breeding process strategies.